♦ 


* 


ORGANIC  CHEMISTRY. 


A  TEXT-BOOK 

OF 

ORGANIC  CHEMISTRY. 


BY 

A.  BERNTHSEN,  Ph.D., 

Director  of  the  Scientific  Department  in  the  Chief  Laboratory  of  the  Baden  Aniline  and 
Alkali  Manufactory,  Ludwigshafen-am-Rhein; 
formerly  Professor  of  Chemistry  in  the  University  of  Heidelberg. 


TRANSLATED  BY 

GEOEGE  M^GOWAN,  Ph.D., 

Demonstrator  in  Chemistry,  University  College  of  N.  Wales,  Bangor. 


THE  ORIGINAL  TEXT  SPECIALLY  BROUGHT  UP  TO  DATE  BY  THE  AUTHOR 
FOR  THIS  EDITION. 

0  ,  IaJ  ■  (RJU^^u^ 


LONDON:  BLACKIE  &  SON,  Limited; 
NEW  YOKK:  D.  VAN  NOSTEAND  COMPANY. 
1892. 


S41 

AUTHOR'S  PREFACE 

TO  THE   GERMAN  EDITION. 


In  lecturing  upon  Organic  Chemistry  in  the  University  of 
Heidelberg,  I  have  felt  more  and  more  each  session  the  desira- 
bility of  being  able  to  place  in  the  hands  of  my  students  a 
small  text-book,  which,  while  not  exceeding  some  thirty  sheets 
in  size,  and  of  which  the  descriptive  portion  was  condensed  as 
far  as  practicable,  should  yet  be  of  a  strictly  scientific  charac- 
ter; a  book  which,  beginning  with  homologous  series,  should 
lay  especial  emphasis  upon  summarizing  the  characteristics  of 
each  class  of  compounds,  and,  wherever  possible,  upon  the 
inductive  development  of  the  theoretical  relations  existing 
between  them. 

The  following  text-book  of  Organic  Chemistry  is  an  attempt 
to  fulfil  these  requirements.  Excepting  in  a  few  cases,  where 
another  arrangement  appeared  to  be  more  suitable,  there  is 
given  here  for  each  class  (after  a  short  general  description)  a 
concise  statement  of  the  occurrence,  general  modes  of  forma- 
tion, constitution  and  isomerides,  and  behaviour  of  the  com- 
pounds in  question.  The  choice  of  the  compounds  described 
has  been  practically  determined  by  the  requirements  of  teach- 
ing. A  number  of  tables  are  incorporated,  which  I  have 
already  found  useful  in  my  lectures,  and  which  are  of  service 
for  summarizing. 

The  treatment  of  the  theoretical  matter  is,  especially  in  the 
first  half  of  the  book,  purely  inductive;  the  isomeric  relations 
of  the  parafiins,  for  instance,  are  first  referred  to  under  butane, 


64643 


vi 


author's  preface. 


and  no  constitutional  formula  of  any  important  compound  is 
given  without  the  grounds  for  it  being  indicated.  The  induc- 
tive method  is  also  retained  even  where,  as  in  the  case  of  the 
theory  of  the  benzene  derivatives,  the  historical  development 
has  run  on  other  lines.  In  accordance  with  this  the  class 
definitions  are  based  not  on  theoretical  but  on  actual  relations. 

Type  of  two  sizes  has  been  employed  in  the  book,  in  order 
that  the  matter  which  is  of  the  greatest  importance,  either  in 
itself  or  for  the  purposes  of  a  general  review,  may  be  readily 
distinguished. 

I  have  deemed  it  advisable  to  give  a  number  of  references 
with  regard  to  points  which  have  a  particular  historical  value, 
and  also  to  some  of  the  more  important  recent  researches, 
especially  where  space  did  not  allow  of  these  being  treated  in 
detail. 

Special  pains  have  been  taken  to  make  the  index  complete. 

I  trust,  therefore,  that  the  book  will  be  found  useful,  not 
only  to  the  student  of  chemistry  proper  on  his  entering  upon 
the  study  of  Organic  Chemistry,  but  also  to  students  of  medi- 
cine and  pharmacy,  whose  requirements  have  been  carefully 
borne  in  mind.  It  should  also  prove  of  service  to  chemists 
engaged  in  technical  work,  who  may  wish  to  obtain  a  short 
survey  of  the  present  state  of  our  science. 

I  should  feel  greatly  obliged,  if  my  readers  would  kindly 
draw  attention  to  any  inaccuracies  of  statement  or  errors  of 
print  which  may  have  crept  into  the  work. 

(Signed)     A.  BERNTHSEN. 

Heidelberg,  Ajpril^  1887. 


AUTHOR'S  PREFACE 

TO  THE  ENGLISH  EDITION. 


The  translation  of  this  book  has  been  carried  out  by 
Dr.  M'Gowan,  who  has  reproduced  the  meaning  of  it  so 
thoroughly  that  I  feel  myself  bound  to  acknowledge  in  an 
especial  manner  the  accuracy  of  the  work,  and  to  express  my 
warm  thanks  to  him  for  the  same. 

The  large  amount  of  new  and  important  matter  in  the 
domain  of  Organic  Chemistry,  which  has  appeared  since  the 
German  edition  of  this  book  was  published,  has  been  specially 
gone  over  for  this  edition,  and  at  the  same  time  the  original 
text  has  been  carefully  revised. 

(Signed)     A.  B. 

Mannheim,  March,  1889. 


TEANSLATOR'S  PREFACE. 


In  introducing  the  English  edition  of  this  text-book,  almost 
nothing  remains  to  be  added  to  what  Professor  Bernthsen  has 
said  in  his  prefaces.  The  proof  slips  had  the  great  advantage 
of  being  carefully  revised  by  himself  after  my  own  corrections 
had  been  made,  which  should  ensure  the  accuracy  of  the  work. 
The  book  has  been  very  well  received  in  Germany,  and  will, 
I  trust,  be  found  equally  acceptable  here. 

GEORGE  M^GOWAN. 

University  College  of  N.  Wales,  Bangor, 
May,  1889. 


TABLE  OF  CONTENTS. 


INTRODUCTION. 

Page 

Qualitative  Analysis,  2 
Quantitative  Analysis,  4 
Calculation  of  the  Formula,  7 
.  Determination  of  Molecular  Weight,        ------  8 

Modes  of  determining  Vapour  Density,    -       -  -       -       -  11 

Polymerism  and  Isomerism,  .   -       -       -       -       -       -       -       -  13 

Chemical  Theories,  -       -       -       -       -       -       -       -       -  -13 

Explanation  of  Isomerism;  determination  of  the  Constitution  of  Or- 
ganic Compounds,     -       -       -       -       -       -       -       -       -  16 

Rational  Formulae,  19 

Homology,  .-----..---20 

Radicles,  22 

Classification  of  Organic  Compounds,  23 

Physical  Properties  of  Organic  Compounds,  .  .  -  -  24-32 
Fractional  Distillation,  27 

Class  I.— METHANE  DERIVATIVES. 
I.  Hydrocarbons,  34 

A.  Saturated  Hydrocarbons,  CnH2a+2)  34 

Isomerism,  Nomenclature,  Constitution,        -       -       -  41 

B.  defines,  CnH2n,  46 

Appendix;  Hydrocarbons,  CnH2a,  with  closed  chain,     -  52 

c.  Acetylene  Series,  CnH2n_2,  53 

D.  Hydrocarbons,  CnH2a_4  and  CnH2a-65        -       -       -       -  57 

II.  Haloid  Substitution  Products  of  the  Hydrocarbons,      -  58 

A.  Of  the  Saturated  Hydrocarbons,  58 

B.  Of  the  Unsaturated  Hydrocarbons,  69 

III.  MoNATOMic  Alcohols,  70 

A.  Monatomic  Saturated  Alcohols,  CnH2a-f-iOH,    -       -       -  71 

Primary,  Secondary  and  Tertiary  Alcohols,    -       -       -  73 
(506)  ^2 


X  CONTENTS. 

Page 

B.  Monatomic  Unsaturated  Alcohols,  CnH2n-i OH,        -       -  86 

C.  Monatomic  Unsaturated  Alcohols,  CnH2n-3  0H,        -       -  88 

IV.  Derivatives  of  the  Alcohols,   88 

A.  Ethers  Proper  (Alcoholic  Ethers),   88 

B.  Thio-alcohols  and  -ethers,        ......  93 

c.  Ethers  of  the  Alcohols  with  Inorganic  Acids,  and  their 

Isomers,       .........  97 

1.  Ethers  of  Nitric  Acid,  99 

2.  Derivatives  of  Nitrous  Acid  : 

a.  Ethers,   100 

(3.  Nitro-derivatives  of  the  Hydrocarbons,   -       -       -  100 

3.  Derivatives  of  Hyponitrous  Acid,   103 

4.  Ethers  of  the  Chlorine  Acids,   103 

5.  Ethers  of  Sulphuric  Acid,   103 

6.  Derivatives  of  Sulphurous  Acid  : 

a.  Ethers,  104 

^.  Sulphonio  Acids,  105 

7.  Ethers  of  Tri-  and  Polybasic  Acids,       -       -       -       -  106 

8.  Alcoholic  Derivatives  of  Hydrocyanic  Acid: 

tt.  Nitriles,  107 

Iso-nitriles,     -       -       -       -       -       -       -       -  109 

D.  Nitrogen  Bases  of  the  Alcohol  Radicles,  -       -       -       -  110 

Appendix:  Hydrazines,  117 

E.  Compounds  of  Phosphorus,  Arsenic,  &c.,  v^^ith  Alcohol 

Kadicles : 

1.  Phosphorus  Compounds,        -       -       -       -       -       -  119 

2.  Arsenic  Compounds,  122 

3.  Antimony,  Boron  and  Silicon  Compounds,      -       -       -  125 

F.  Metallic  Compounds  of  the  Alcohol  Radicles,   -       -       -  126 

V.  Aldehydes  and  Ketones,  -  128 

A.  Aldehydes,  129 

B.  Ketones,  -  138 

VI.  Monobasic  Eatty  Acids,  146 

A.  Saturated  Acids,  C^HonO-i,  146 

B.  Unsaturated  Acids,  Cn  Hon-o  0-2,  164 


CONTENTS.  xi 

Page 

c.  Propiolic  Acid  Series,  CnH2n-4  02,   167 

D.  Substitution  Products  of  the  Monobasic  Acids,        -       -  168 

VII.  Acid  Derivatives,   173 

A.  Ethers  of  the  Patty  Acids,   174 

B.  Chlorides  of  the  Acid  Kadicles,   176 

c.  Acid  Anhydrides,   178 

D.  Thio-acids  and  Thio-anhydrides,   179 

E.  Amides,   180 

F.  Amido-  and  Imido-chlorides,   183 

G.  Thiamides  and  Imido-thio-ethers,   184 

H.  Amidines,       -   185 

Amidoximes,   186 

viii.  Polyatomic  Alcohols,   187 

A.  Glycols,  ...    187 

Derivatives,  -       -       -       -       -       -       -       -  -187 

Amines  of  the  Diatomic  Alcohols,   193 

B.  Triatomic  Alcohols,  -       -       -       -       -       -       -       -  198 

c.  Tetra-,  Penta-  and  Hexatomic  Alcohols,  -       .       -       -  202 

Oxidation  Products  of  the  Polyatomic  Alcohols,    -       -  204 

IX.  Polyatomic  Monobasic  Acids,   206 

A.  Diatomic  Monobasic  Acids,   206 

Amido-acids,   212 

Lactic  Acids,   214 

Appendix:  Lactones,        -       -       •       -       -       -  218 

b.  Tri-  to  Hexatomic  Monobasic  Acids,        -       -       -       -  219 

C.  Aldehyde-alcohols,   220 

D.  Ketone-alcohols,   221 

E.  Diatomic  Aldehydes,   221 

F.  Diatomic  Ketones,   221 

G.  Ketone-aldehydes,   222 

H.  Monobasic  Aldehyde-acids,   222 

I.  Monobasic  Ketonic  Acids,   222 

X.  Dibasic  Acids,   227 

A.  Saturated  Diatomic  Dibasic  Acids,   228 

b.  Unsaturated  Diatomic  Dibasic  Acids,      .       -       -       .  236 


xii  CONTENTS. 

Page 

c.  Triatomic  Dibasic  Acids,  -       -       -       -       -       -       -  238 

D.  Tetratomic  Dibasic  Acids,       ------  240 

E.  Penta-  and  Hexatomic  Dibasic  Acids,      .       -       .       -  243 

F.  Dibasic  Ketonic  Acids,  244 

XI.  Tri-  to  Hexabasic  Acids,  245 

A.  Triatomic  Tribasic  Saturated  Acids,        .       .       .       .  245 

B.  Unsaturated  Acids,  --------  246 

c.  Tetratomic  Tribasic  Acids,  •     -  246 

D.  Pentatomic  Tribasic  Acids,      ------  247 

E.  Tetra-,  Penta-  and  Hexabasic  Acids,        .       .       -       -  247 

XII.  Cyanogen  Compounds,   248 

A.  Cyanogen  and  Hydrocyanic  Acid,     -       -       -       -       .  249 

B.  Halogen  Compounds  of  Cyanogen,    .       -       -       -       -  257 

C.  Cyanic  and  Cyanuric  Acids,     -       -       -       -       -       -  257 

D.  Thiocyanic  Acid  and  its  Derivatives,        -       -       -       -  261 

E.  Cyanamide  and  its  Derivatives,  -  -  -  -  -  264 
r.  Appendix :  Theoretical  Considerations  as  to  Isomerism  in 

the  Cyanogen  Group,    -       -       -       -       -       -       -  265 

XIII.  Carbonic  Acid  Derivatives,  266 

A.  Ethers  of  Carbonic  Acid,  267 

B.  Chlorides  of  Carbonic  Acid,  268 

c.  Amides  of  Carbonic  Acid,        -  -       -  .  269 

Ureides,   272,  279 

D.  Sulphur  Derivatives  of  Carbonic  Acid,     -       -       -       -  274 

E.  Amidines  of  Carbonic  Acid,     ------  277 

F.  Uric  Acid  Group,    -       -       -  279 

XIV.  Carbohydrates,  285 

A.  The  Grape  Sugar  Group,  285 

B.  The  Cane  Sugar  Group,  289 

C.  The  Cellulose  Group,  292 

XV.  Transition  to  the  Aromatic  Compounds,    -      -      -      -  295 

A.  Tri-,  Tetra-  and  Penta-methylenes,  -----  295 

B.  Furfurane,  Thiophene  and  Pyrrol,  -  -  -  -  -  297 
c.  Pyrazols  and  Thiazols,  -       -  302 


CONTENTS.  xiii 
Class  II.— BENZENE  DERIVATIVES. 

Page 

XVI.  Summary,   303 

Differences  between  the  Benzene  and  Fatty  Hydrocarbons,  306 

Isomeric  Relations,   307 

Proof  of  the  Equal  Value  of  the  Six  Hydrogen  Atoms,  -  307 
Proofs,  that  for  every  H-atom  (a),  two  other  pairs  of 

symmetrically  linked  H-atoms  exist,  -       -       -       -  308 

Constitution  of  Benzene,   -       -       -       -       -       -       -  311 

Determination  of  Position,        -       -       -       -       -       -  313 

Special  Benzene  Formulae,        -       -       -       -       -       -  316 

Laws  Governing  Substitution,  -       -       -       -       -       -  317 

Further  Isomerism,  -       -       -       -       -       -       -       -  318 

Occurrence  of  the  Benzene  Derivatives,     -       -       -       -  319 

Modes  of  Formation  of  the  Benzene  Derivatives,       -       -  320 

XVII.  Benzene  Hydrocarbons,  323 

A.  Saturated  Hydrocarbons,  323 

B.  Unsaturated  Hydrocarbons,  ------  331 

xviii.  Haloid  Substitution  Products,  332 

XIX.  Nitro-substitution  Products,  336 

XX.  Amido-derivatives,  340 

A.  Primary  Monamines,  342 

B.  Secondary  Monamines,  346 

c.  Tertiary  Monamines,  348 

D.  Quaternary  Bases,        -       -       -       -       -       -       -  348 

E.  Diamines,  Triamines,  &c.,  349 

Aniline,  350 

Substitution  Products  of  Aniline,   -       -       -       -  352 

Alkylated  Anilines,  353 

Di-  and  Tri-phenylamines,  355 

Colour  Derivatives  of  Diphenylamine,    -       -       -  355 

Anilides,  357 

Homologues  of  Aniline,     ------  358 

Diamines,  Triamines,  &c.,  359 


xiv  CONTENTS. 

Page 

XXI.  DiAZO-  AND  AZO-COMPOUNDS ;  HYDRAZINES,  -         -  360 

A.  Diazo-compounds,        -       -       -       -       -       -       -  360 

B.  Diazo-amido-compounds,  364 

C.  Azo-compounds,  366 

1.  Azoxy-compounds,  -  366 

2.  Hydrazo-compounds,      -       -       -       -       -       -  367 

3.  Azo-compounds,   367 

4.  Amido-azo-  and  Oxy-azo-compounds,      -       -       -  368 

D.  Hydrazines,   372 

XXII.  Aromatic  Sulphonic  Acids,   373 

XXIII.  Phenols,   376 

A.  Mon atomic  Phenols,  -  378 

Phenol,  -  381 

Derivatives  of  Phenol,   382 

Homologues  of  Phenol,  -       -       -       -       -       -  387 

B.  Diatomic  Phenols,        -   388 

c.  Triatomic  Phenols,   391 

D.  Tetra-,  Penta-  and  Hexatomic  Phenols,        -       -       -  392 

E.  Quinones,   392 

F.  Quinone  Chlor-imides,  -       -  395 

XXIV.  Aromatic  Alcohols,  Aldehydes  and  Ketones,      -      -  395 

A.  Aromatic  Alcohols,      -       -       -       -       -       -       -  395  . 

B.  Aromatic  Aldehydes,   398 

c.  Aromatic  Ketones,      -  -       -       -       -       .  399 

D.  Oxy-alcohols  and  -aldehydes;  Ketone-alcohols,     -       -  400 

XXV.  Aromatic  Acids,  -      -  401 

Summary,   401 

A.  Monobasic  Aromatic  Acids,  ------  409 

1.  Monatomic  Saturated  Acids,  -       -       -       -       -  412 

Benzoic  Acid,   412 

2.  Monatomic  Unsaturated  Acids,       -       -       -       -  417 

3.  Diatomic  Saturated  Phenolic  Acids,        -       -       -  419 

4.  Alcohol- acids  and  Ketone-acids,      -       -       -       -  422 

5.  Tri-  and  Polyatomic  Phenolic  Acids,       -       -       -  425 

6.  Unsaturated  Phenolic  Acids,   427 


CONTENTS.  .  XV 

Page 

B.  Dibasic  Acids,  ...  ^  -  -  -  -  428 
c.  Tri-  to  Hexabasic  Acids,  430 

XXVI.  Indigo  (or  Indole)  Group,  431 

Indigo,  431 

Derivatives  of  Indigo,       -       -  433 

Indole,  436 

XXVII.  DiPHENYL  Group,  438 

Diphenyl,  438 

Diphenyl  Derivatives,  439 

XXVIII.  DiPHENYL-METHANE  GROUP,  442 

Diphenyl-methane,  442 

Benzophenone,  444 

Homologues  of  Diphenyl-methane ;  Fluorene,   -       -       -  445 

XXIX.  Triphenyl-methane  Group,   446 

Triphenyl-methane,   446 

Triphenyl-methane  Dyes,  448 

1.  Diamido-triphenyl-methane  Group,  -       .       -       -  449 

2.  Eosaniline  Group,   450 

8.  Trioxy- triphenyl-methane  Group,    -       -       -       -  454 

4.  Triphenyl-methane-carboxylic  Acid  (the  Eosin Group),  455 

XXX.  DiBENZYL  Group,  457 

Appendix:  Diphenyl-diacetylene,  459 

COMPOUNDS  WITH  CONDENSED  BENZENE  NUCLEI. 

XXXI.  Naphthalene  Group,  460 

Naphthalene,   460 

Derivatives  of  Naphthalene,  463 

Homologues;  Carboxylic  Acids,       .       .       -       .       -  457 

Appendix:  Indonaphthene;  Thiophthene,  -       -       -       -  468 

XXXII.  Anthracene  and  Phenanthrene  Groups,       -      -       -  469 

a.  Anthracene,  469 
Derivatives  of  Anthracene,  -       -       -       -       -       -  471 

Alizarin,  474 


xvi  CONTENTS. 

Page 

B.  Phenanthrene,     -       -       -       -       -       -       -       -  475 

c.  Hydrocarbons  of  more  Complex  Nature,       -       -       -  477 
Eluoranthene;  Pyrene;  Chrysene;  Ketene,  -       -       -  477 

PYRIDINE  DERIVATIVES,  ALKALOIDS  AND  COMPOUNDS 
RELATED  TO  THEM. 

General  Characters;  Summary,  478 

xxxiii.  Pykidine  Group,  481 

Pyridine,  485 

Homologues  of  Pyridine,  -------  486 

Pyridine-carboxylic  Acids,  487 

Hydro-derivatives,  488 

Appendix;  Pyrone  Group;  Ketines,  491 

XXXIV.  QUINOLINE  AND  ACRIDINE  GROUPS,  491 

A.  Quinoline  Group,  491 

Quinollne,  495 

Homologues;  Condensed  Quinolines,    -       .       -       .  496 

Quinoline-carboxylic  Acids,  497 

Bases  related  to  Quinoline,  497 

B.  Acridine  Group,  498 

c.  Alkaloids  of  Unknov^rn  Constitution,     -       -       -       -  499 

{a)  Opium  Bases,  499 

(6)  Cinchona  Bases,  500 

(c)  Strychnine  Bases,  500 

{d)  Solanine  Bases,     -       -       -       -       1.       .       .  501 

D.  Phenazine  Group,  501 

Phenazine,  501 

Toluylene  Red,  502 

Safranines,  503 

Appendix;  Dyes  of  Unknown  Constitution,        -       -  503 

XXXV.  Terpenes  and  Camphors,  504 

Ethereal  Oils,  504 

A.  Terpenes,  504 

B.  Camphors,   -  509 


CONTENTS.  xvii 

Page 

XXXVI.  Eesins;  G-LucosiDES;  Vegetable  Substances  (of  Un- 
known Constitution),  -  511 

A.  Resins,        -       -       -       -       -       -       -       -       -  511 

B.  Glucosides,   512 

c.  Vegetable  Substances  of  Unknown  Constitution,  -       -  513 

XXXVII.  Albuminous  Substances;  Animal  Chemistry,  -       -       -  514 

A.  Albumens,  515 

B.  Albumenoids,       -       -       -       -       -       -       -       -  517 

C.  Compounds  of  a  Higher  Order  than  Albumen,      -       -  519 

D.  Substances  produced  during  Metabolic  Processes,  -       -  519 

INDEX,        .       -   521 


ADDITIONS  AND  COREEOTIONS. 


Page  15,  line  8  from  foot. 

In  case  the  above  sentence  should  have  the  effect  of  unintentionally 
causing  the  reader  to  undervalue  the  work  of  Kolbe  and  FranJcland  on 
this  subject,  I  would  (with  the  author's  concurrence)  refer  him  for 
further  details  to  Kopp^s  "  Entwickelung  der  Chemie  in  der  neueren 
Zeit"  (Miinchen,  1873),  and  to ^.  Meyer^s  "Geschichte  der  Chemie" 
(Leipzig,  1889).  —Trans. 

Page  86,  line  1. 

For   "  Methyl-ethyl-caebinol  "   read   "  Methyl-ethyl-carbin- 

CARBINOL." 

Page  221,  after  line  4  from  foot: 

"Diaterebic  acid  is  unknown  in  the  free  state.  Its  lactone  is 
Terebic  acid,  C7H10O4,  which  results  from  the  oxidation  of  oil  of  tur- 
pentine with  chromic  acid  mixture." 

Page  222,  after  line  18  read: 

Pyroracemic  aldehyde,  CH3  -  CO  -  CHO,  can  be  prepared  from 
isonitroso-acetone,  just  as  di-acetyl  can  from  methyl-isonitroso-acetone. 

Page  274,  foot  of. 

The  names  of  the  compounds  in  this  table  are  as  nearly  as  possible 
literal  translations  from  the  German. 

Page  281,  line  5  from  foot. 

After  ''Parabanic  acid"  read    oxalyl  urea.''^ 

Page  403,  after  line  9  read : 

e.g.   CeHs  -  CH  =  CH  -  CO2H  CsHs  -  C  =  C  -  COoH 

Cinnamic  acid.  Phenyl-propiolic  acid. 

Page  482,  after  line  23: 

'^Piperidine  is  therefore  also  termed  Pentamethylene-imine." 


ABBREVIATIONS. 


A.  —  Liebig's  Annalen  der  Chemie. 

Ann.  Chim.  Phys.  =  Annales  de  Chimie  et  de  Physique. 
Arch.  f.  Phys.  —  Archiv  f tir  Physiologie. 

B.  =  Berichte  der  Deutschen  Chemischen  Gesellschaft. 
Ch.  Soc.  J.  =  Journal  of  the  Chemical  Society. 

J.  pr.  Ch.  —  Journal  fur  Praktische  Chemie. 

Monats.  f.  Chemie  =  Monatshefte  fiir  Chemie  und  verwandte 

Theile  anderer  Wissenschaften. 
Z.  Anal.  Ch.  =  Zeitschrif t  fiir  Analytische  Chemie. 
(  °)  or  B.  Pt.=:  Boiling  Point. 
[  °]  or  M.  Pt.  =  Melting  Point. 


OEGANIC  CHEMISTRY. 


INTRODUCTION. 

^  Organic  Chemistry  is  the  Chemistry  of  the  Carbon  Com- 
pounds. Formerly  those  compounds  which  occur  in  the 
organic,  i.e,  the  animal  and  vegetable,  worlds  were  classed 
under  Organic,  and  those  which  occur  in  the  mineral  world 
under  Inorganic  Chemistry,  the  first  to  adopt  this  arrangement 
having  been  Lemery  in  his  Cours  de  Chimie  (1675).  After  the 
recognition  of  the  fact  that  all  organic  substances  contain  car- 
bon, it  was  thought  that  the  difference  between  organic  and 
inorganic  compounds  could  be  explained  by  saying  that  the 
latter  were  capable  of  preparation  in  the  laboratory,  but  the 
former  only  in  the  organism,  under  the  influence  of  a  particular 
force,  the  life  force — vis  vitalis — (Berzelius).  But  this  assump- 
tion was  rendered  untenable  when  Wohler  in  1828  synthetically 
prepared  urea,  CONgH^,  a  typical  secretion  of  the  animal 
organism,  from  cyanic  acid  and  ammonia,  two  compounds 
which  were  at  that  time  held  to  be  inorganic;  and  when, 
shortly  afterwards,  the  synthesis  of  acetic  acid,  by  the  use  of 
carbon,  sulphur,  chlorine,  water  and  zinc,  was  effected. 

Since  then  so  many  syntheses  of  this  kind  have  been  achieved 
as  to  prove  beyond  doubt  that  the  same  chemical  forces  act 
both  in  the  organic  and  inorganic  worlds. 

The  separation  of  the  two  branches.  Organic  and  Inorganic 
Chemistry,  from  each  other  is,  however,  still  retained  for  con- 
venience sake,  although  the  original  reasons  for  this  separation, 
which  at  the  time  was  more  or  less  a  matter  of  necessity,  have 
since  been  found  to  be  erroneous.  In  consequence  of  the  great 
capability  for  combination  which  carbon  possesses,  the  number 
of  organic  compounds  is  extraordinarily  large,  and  in  order  to 

(506)  A 


2 


INTRODUCTION. 


be  in  a  position  to  study  them,  it  is  necessary  to  have  a  know- 
ledge of  the  other  elements,  including  the  metals.  The  carbon 
compounds,  many  of  the  most  important  of  which  contain  only 
carbon  and  hydrogen,  or  carbon,  hydrogen,  and  oxygen,  also 
stand  in  a  closer  relationship  to  each  other  than  do  the  com- 
pounds of  the  other  elements.  Partly  upon  grounds  of  con- 
venience, carbon  itself  and  some  of  its  principal  compounds, 
such  as  carbonic  acid,  which  is  so  widely  distributed  in  the 
mineral  kingdom,  are  treated  of  under  Inorganic  Chemistry. 

One  must  not  confound  the  terms  "organic"  and  '^organized"  bodies;  the 
latter,  e.g.  leaves,  nerves  and  muscles,  and  also  the  life-processes  which  go 
on  in  the  interior  of  the  organism,  are  treated  of  under  Physiology  and 
Physiological  Chemistry. 

Constituents  of  the  Carbon  Compounds. 

Many  organic  substances  are  made  up  of  carbon  and  hydro- 
gen alone,  such  being  termed  hydrocarbons,  for  instance,  ethy- 
lene, benzine,  petroleum,  benzene,  naphthalene,  and  oil  of  tur- 
pentine; a  vast  number  consist  of  carbon,  hydrogen,  and  oxy- 
gen, for  instance,  wood  spirit,  alcohol,  glycerine,  aldehyde,  oil 
of  bitter  almonds,  formic  acid,  acetic  acid,  stearic  acid,  tartaric 
acid,  benzoic  acid,  carbolic  acid,  tannic  acid,  and  alizarin; 
many  (chiefly  basic)  compounds  contain  carbon,  hydrogen,  and 
nitrogen,  for  instance,  prussic  acid,  aniline,  and  conine;  as 
examples  of  compounds  containing  carbon,  hydrogen,  nitrogen, 
and  oxygen,  may  be  taken  urea,  uric  acid,  indigo,  morphine, 
and  quinine.  In  addition  to  these,  sulphur,  chlorine,  bromine, 
iodine,  phosphorus,  and,  generally  speaking,  the  larger  number 
of  the  more  important  elements,  are  also  frequent  constituents 
of  the  carbon  compounds. 

Qualitative  Analysis  of  Organic  Compounds. 

The  presence  of  Carbon  in  a  compound  is  often  proved  by 
the  "carbonization"  of  the  latter,  e.g.  starch,  sugar,  &c.,  when 
heated  in  a  glass  tube,  or  when  concentrated  sulphuric  acid  is 
poured  over  it.    Those  compounds  which  boil  without  decom- 


QUALITATIVE  ANALYSIS. 


3 


position  deposit  carbon  when  their  vapours  are  led  through  a 
red-hot  tube.  But  the  best  proof  of  the  presence  of  carbon 
is  obtained  by  completely  oxidizing  the  organic  compound  by 
either  heating  it  with  copper  oxide  (see  below),  or  by  leading 
its  vapour  over  the  glowing  oxide.  The  carbon  present  is  thus 
converted  into  carbon  dioxide,  and  the  Hydrogen  into  water. 
Nitrogen  in  organic  compounds  is  recognized — 
(a)  Frequently  by  a  smell  resembling  that  of  burnt  hair, 
upon  heating; 

(h)  Frequently  by  the  presence  of  red  fumes,  or  by  explosion, 
upon  heating  (nitro-  and  diazo-compounds) ; 

(c)  In  most  cases  by  the  liberation  of  ammonia  upon  heating 
with  soda-lime  (/FoA/gr); 

{d)  In  all  cases  by  heating  with  potassium  (and  in  most 
cases  with  sodium),  and  testing  the  metallic  cyanide  formed 
— (see  Cyanogen  Compounds) — by  dissolving  the  melted  mass  in 
water,  adding  alkali  and  a  few  drops  of  ferrous  sulphate  and 
ferric  chloride  solutions,  boiling,  and  saturating  with  hydro- 
chloric acid  (formation  of  Prussian  Blue);  or  by  converting  the 
cyanide  into  sulphocyanide,  and  proving  the  presence  of  the 
latter  by  means  of  the  blood-red  coloration  with  ferric  chloride. 
[See  tests  for  hydrocyanic  acid  (Lassaigne).]  If  sulphur  be 
likewise  present,  iron  filings  must  be  added. 

Testing  for  the  Halogens.  Direct  addition  of  nitrate  of  silver 
is  usually  not  practicable;  thus,  no  chlorine  can  be  detected 
in  chloroform  even  upon  boiling  it  with  AgNOg.  The  halogens 
are  therefore  tested  for: 

(a)  By  heating  the  substance  on  a  platinum  wire  with  cupric 
oxide  in  the  Bunsen  flame,  or  by  causing  the  vapour  of  the 
compound  to  pass  over  glowing  copper  gauze;  in  this  way 
chlorine  gives  first  a  blue  and  then  a  green  flame  coloration, 
and  iodine  a  green  (Beilstein); 

(b)  By  heating  the  substance  strongly  with  pure  lime,  and 
testing  the  haloid  calcium  salt  produced  with  silver  nitrate, 

(c)  By  heating  in  a  sealed  tube  with  fuming  nitric  acid  and 
nitrate  of  silver,  when  the  haloid  silver  salt  is  produced 
(Carius), 


4 


INTRODUCTION. 


Testing  for  Sulphur: 

(a)  In  many  cases,  upon  boiling  with  an  alkaline  solution 
of  lead  oxide,  brown  sulphide  of  lead  is  formed  {e.g.  white  of 

egg); 

(h)  By  heating  with  sodium,  and  testing  the  sodium  sulphide 
formed  with  water  upon  a  silver  coin  (black  stain);  or  by 
means  of  sodium  nitroprusside  (purple -violet  coloration), 
(Schonn) ; 

(c)  By  complete  oxidation  in  the  dry  way,  by  fusing  with 
potassium  hydrate  and  nitre,  or  by  heating  with  mercuric 
oxide  and  sodic  carbonate;  or  in  the  wet  way,  by  fuming  nitric 
acid  (Carius),  and  testing  the  sulphuric  acid  produced,  by 
chloride  of  barium. 

In  like  manner  Phosphorus  is  converted  by  complete  oxida- 
tion into  phosphoric  acid;  or,  upon  heating  with  powdered 
magnesia,  and  moistening  the  resulting  mass  with  water,  the 
presence  of  phosphu retted,  hydrogen  can  be  recognized  (Schonn). 

All  the  other  Elements  are  tested  for,  after  complete  oxida- 
tion of  the  compound  (preferably  by  Carius^s  method),  in  the 
usual  way. 

Quantitative  Organic  or  Elementary  Analysis. 

A.  Estimation  of  Carbon  and  Hydrogen  (Combustion).  The 
substance  is  oxidized  by  heating  it  to  redness  with  cupric 
oxide  {Liehig)y  or  with  other  substances  which  readily  give  up 
oxygen,  such  as  lead  chromate,  platinum  asbestos  and  oxygen 
(Kojyfer),  &c.,  in  a  tube  of  difficultly  fusible  glass,  which  is  open 
either  at  one  or  at  both  ends. 

The  carbon  dioxide,  thus  produced  by  the  oxidation  of  the 
carbon,  is  absorbed  by  a  moderately  concentrated  solution  of 
caustic  potash  contained  in  specially  shaped  bulbs  (Llebig,  Mohr, 
MitsclierUch,  JVinJder,  &c.),  and  the  water,  produced  by  the  oxi- 
dation of  the  hydrogen,  in  a  U-shaped  chloride  of  calcium  tube, 
both  tubes  being  weighed  before  and  after  the  combustion.  If 
the  substance — (0*2  to  0*3  grm.) — is  solid,  it  is  either  mixed 
with  tine  copper  oxide  (Liebig,  Bunsen,)  or  placed  in  a  porcelain 


ELEMENTARY  ANALYSIS. 


5 


or  platinum  boat  and  burnt  in  a  stream  of  air  or  oxygen  (open 
tube).  Liquids  are  weighed  out  in  small  thin  sealed  glass  bulbs. 
When  nitrogen  is  present,  a  spiral  of  copper-foil  is  placed  in  the 
front  part  of  tlie  combustion  tube  and  heated  to  redness,  in 
order  to  reduce  any  oxides  of  nitrogen  which  may  be  formed 
in  the  subsequent  combustion.  In  the  presence  of  sulphur  or 
of  the  halogens,  lead  chromate,  which  has  been  fused  and  then 
powdered,  is  used  instead  of  copper  oxide,  so  as  to  convert  any 
CI,  SO2,  &c.,  into  Pb  CI2,  Pb  SO^,  &c.,  and  so  to  prevent  them 
from  passing  into  the  potash  solution.  When  only  halogens, 
without  sulphur,  are  present,  the  combustion  is  carried  out 
with  copper  oxide,  a  copper,  or  still  better  a  silver  spiral,  which 
is  kept  cool,  being  placed  in  the  fore-part  of  the  tube  to  retain 
the  halogens. 

In  the  presence  of  alkalies  or  alkaline  earths  (which  would 
retain  carbon  dioxide),  lead  chromate  mixed  with  y^^h  of  its 
weight  of  potassic  bichromate  is  used;  the  chromic  acid  then 
expels  all  the  carbonic  acid. 

Explosive  compounds  must  be  burnt  in  a  vacuum.  From 
the  weights  of  carbon  dioxide  and  water  found,  the  percentages 
of  C  and  H  are  readily  calculated: 

B.  Estimation  of  Nitrogen.  This  estimation  is  either  rela- 
tive or  absolute.  In  the  former  case  the  proportion  between 
the  nitrogen  and  the  carbonic  acid  evolved  is  determined 
(Liehig,  Bunsen);  in  the  latter  the  nitrogen  is  either  estimated 
as  such  volumetrically,  or  as  ammonia. 

The  conversion  into  Ammonia  is  effected  by  heating  the 
substance  strongly  with  soda-lime  (Will,  Varrentrap),  or  by 
treating  it  with  strong  sulphuric  acid  and  permanganate  of 
potash  (Kjeldahl;  Z.  Anal.  Ch.  22.  366;  also  B.  19,  R.  852). 
The  ammonia  is  then  either  titrated  directly,  or  transformed 
into  the  double  chloride  of  ammonium  and  platinum  (NH^  Cl)2 
Pt  CI4,  which  is  then  weighed,  or  else  ignited,  and  the  weight 
of  the  residual  metallic  platinum  noted. 


6 


INTRODUCTION. 


In  the  Volumetric  Estimation  of  Nitrogen  the  substance  is 
mixed  with  copper  oxide,  a  copper  spiral  being  also  used,  and 
the  combustion  is  carried  out  in  the  usual  way,  but  in  a  stream 
of  carbonic  acid;  the  CO^  is  either  generated  from  magncsite 
in  the  tube  itself,  or  led  through  it.  The  nitrogen  is  collected 
over  mercury  and  aqueous  caustic  potash  (Dumas),  or  directly 
over  potash  (Zulkowsky,  Schwarz,  Schiff,  &c.). 

Its  percentage  is  got  from  the  formula — 

N  (per  cent.)  =  V  •  •         •  0-001256  •  ^ 

where  V  =  the  volume  of  the  nitrogen, 
b  =  the  barometric  pressure 
t  =  the  temperature, 
w  =  the  tension  of  the  water  vapour, 
0'001256  =  the  weight  of  a  normal  cubic  centimeter  of  nitrogen, 
and  g  =  the  weight  of  the  substance  taken 

The  volumetric  method  is  available  in  every  case,  but  the 
other  (ammonia)  method  not  always,  not,  for  instance,  in  the 
case  of  nitro-compounds,  of  many  organic  bases,  &c.,  the  nitro- 
gen of  these  not  being  completely  transformed  into  ammonia 
upon  heating  with  soda-lime. 

For  the  simultaneous  determination  of  carbon,  hydrogen,  and  nitrogen, 
the  combustion  must  be  carried  on  in  a  stream  of  pure  oxygen,  the  mixture 
of  gases  escaping  from  the  potash  bulbs  being  collected  over  a  solution 
of  chromous  chloride,  which  absorbs  the  oxygen  but  not  the  nitrogen 
(B.  19.  R  710). 

C.  Estimation  of  Sulphur  and  Phosphorus.    The  Sulphur 

is  estimated  as  sulphuric  acid,  being  converted  into  this — 

(a)  in  the  wet  way,  by  heating  the  substance  with  fuming 
nitric  acid  to  150°-250°  in  a  sealed  tube  (Carius),  or  in  a  mixed 
stream  of  nitric  oxide  and  oxygen  or  nitric  acid  vapour  in  a 
combustion  tube  (Claesson); 

(h)  in  the  dry  way — (and  this  method  is  only  available  in 
the  case  of  the  less  volatile  compounds) — by  fusing  the  sub- 
stance with  potassic  hydrate  and  nitre,  or  with  soda  and 


CALCULATION  OF  KORMUL^E. 


7 


chlorate  or  cliromate  of  potash,  also  by  heating  with  soda  and 
mercuric  oxide,  or  with  lime  in  a  stream  of  oxygen,  and  so  on; 

(c)  by  burning  in  a  stream  of  oxygen  and  collecting  the  SO2  formed  in 
hydrochloric  acid  containing  bromine  {Sauer). 

Phosphorus  is  estimated  by  analogous  methods. 

D.  Estimation  of  the  Halogens.  Here  also  the  organic  sub- 
stance is  completely  decomposed — 

(a)  after  Carius,  as  above,  in  a  sealed  tube,  with  addition  of 
silver  nitrate,  by  which  means  the  halogen  is  converted  into 
its  silver  salt; 

(b)  by  heating  the  compound  strongly  with  pure  lime  in  a 
hard  glass  tube,  or  in  two  crucibles,  one  of  which  is  inverted 
in  the  other,  or  with  sodic  carbonate  and  nitre  in  a  tube.  The 
chloride  formed  is  precipitated  with  silver  nitrate  in  the  usual 
way; 

(c)  by  the  action  of  nascent  hydrogen  (sodium  amalgam),  the 
halogen  in  the  organic  substance  can  frequently  be  converted 
into  its  hydrogen  compound  {KekuU), 

E.  Inorganic  Bases  and  Acids,  contained  in  organic  salts, 
can  often  be  estimated  directly  by  the  usual  methods. 

F.  Oxygen  is  almost  invariably  determined  by  difference ;  direct  methods 
of  estimation  have  been  proposed  by  Baumhauer,  Ladenhurg,  Stromeyer, 
and  others. 

The  limit  of  error  in  an  estimation  of  carbon  is  about  0*05 
to  0*1  p.c,  in  one  of  hydrogen  +  0*1  to  0*2  p.c,  while  in  the 
volumetric  estimation  of  nitrogen  several  tenths  p.c.  too  much 
are  easily  found. 

The  Calculation  of  the  Formula. 

The  same  principle  applies  here  as  in  the  case  of  inorganic 
compounds,  i,e,  the  percentage  numbers  found  are  divided  by 
the  atomic  weights  of  the  respective  elements,  the  relative  pro- 
portions of  the  quotients  obtained  being  expressed  in  whole 
numbers.  For  instance,  acetic  acid  being  found  to  contain 
40*11  p.c.  carbon,  6*80  p.c.  hydrogen,  and,  consequently,  53*09 


8 


INTRODUCTION. 


p.c.  oxygen,  the  quotients  are  to  each  other  as  3*34  :  6*80  :  3*32 
=  1:2:1.  The  simplest  analysis-formula  of  acetic  acid  would 
therefore  be  CHgO.  Sometimes  figures  are  obtained  which 
correspond  with  equal  nearness  to  different  formulae,  between 
which  it  is  therefore  impossible,  without  further  data,  to  choose. 

For  instance,  a  sample  of  naphthalene  yields  on  analysis  93*70  p.c.  carbon 
and  6'30  p.c.  hydrogen;  the  quotient  proportion  here  is  7*81  to  6*30  = 
1*239  : 1,  which  corresponds  equally  well  with  the  numbers  5  :  4  or  11  : 9. 
The  formula  C5H4  requires  93*75  p.c.  carbon  and  6*25  p.c.  hydrogen,  and 
the  formula  CnHo,  93*62  p.c.  carbon  and  6*38  p.c.  hydrogen,  the  deviations 
from  the  actual  numbers  found  being  in  both  cases  within  the  limits  of 
experimental  error.  Therefore  other  considerations  must  be  taken  into 
account  here,  in  order  to  decide  between  the  two  formulae. 

Even  in  simple  cases,  such  as  that  of  acetic  acid,  the  formula 
found  (CH2O)  is  not  to  be  taken  as  the  molecular  formula 
without  further  proof;  it  only  expresses  the  atomic  number 
proportions.  The  molecular  formula  has  to  be  determined 
according  to  special  principles. 

Determination  of  Molecular  Weight. 

Our  chemical  formulae  {e.g.  CH2O)  express  not  merely  a 
percentage  relation,  but  at  the  same  time  the  smallest  quantity 
of  the  compound  which  is  capable  of  existing  as  such,  i.e.  a 
molecule  of  it.  This  molecule  is  ideally  no  longer  divisible  by 
mechanical  means,  but  only  by  chemical,  and  then  into  its  con- 
stituent atoms.  If  the  formula  CH^O  were  the  correct  one  for 
acetic  acid,  then  the  amount  of  oxygen  (or  carbon)  contained  in 
a  molecule  would  be  indivisible,  and  that  of  hydrogen  divisible 
only  by  2.  Since,  however,  it  has  been  observed  that  one-fourth 
of  the  total  hydrogen  in  acetic  acid  is  replaceable,  e.g.  by  a 
metal,  with  the  formation  of  a  salt,  it  is  obvious  that  the  quan- 
tity of  hydrogen  in  the  molecule  must  be  divisible  by  4,  and  so 
the  formula  must  contain  at  least  4  atoms  of  hydrogen,  and 
must  therefore  be  C^f>^,  or  some  multiple  of  it.  This  is,  in 
fact,  the  case.  Acetate  of  silver  contains  64*67  p.c.  silver,  and 
therefore  35-33  p.c.  of  the  acetic  acid  radicle;  or,  to  1  atom  of 
silver  =108  parts  by  weight,  there  are  59  parts  by  weight  of 
the  acid  radicle.  This  59,  together  with  1  atom  of  hydrogen  =  1, 


DETERMINATION  OF  MOLECULAR  WEIGIir. 


9 


makes   the    molecular  weight  of   acetic   acid    60,  =  2  x  30, 

This  is  a  determination  of  molecular  weight  by  chemical 
means.  Such  determinations  are  carried  out  in  the  case  of 
acids  generally  by  means  of  their  silver  salts,  which  are  usually 
constituted  normally,  are  easy  to  purify,  are  almost  always 
free  from  water  of  crystallization,  and  are  readily  analysed. 
One  only  requires  to  know  here  whether  the  acid  is  mono-  or 
polybasic.  In  the  case  of  a  di-,  tri-,  &c.,  basic  acid,  the  above 
calculation  must  be  made  with  reference  to  2,  3,  &c.,  atoms  of 
silver,  whereas  acetic  acid^ — being  monobasic — contains  only 
one  replaceable  atom  of  hydrogen,  which  is  therefore  exchanged 
for  one  atom  of  silver.  Consequently,  its  formula  cannot  be 
a  multiple  of  C2H^02. 

In  the  determination  of  the  molecular  weight  of  Bases,  their 
platinum  salts  are  similarly  made  use  of,  these  being  almost 
always  constituted  on  the  type  of  platinum-ammonium  chloride : 
(]SrH^Cl)2,  PtCl^:  i.e.  they  contain  two  molecules  of  hydro- 
chloric acid  and  one  molecule  platinic  chloride  to  every  two 
molecules  of  a  mono-acid,  or  to  one  molecule  of  a  di-acid  base. 

To  determine  the  molecular  weight  of  Indifferent  Com- 
pounds, derivatives  must  be  prepared  and  examined  for  the 
proportion  of  the  total  hydrogen  which  is  replaceable,  e.g.,  by 
chlorine.  For  example,  by  the  action  of  chlorine  upon  naph- 
thalene, there  is  first  formed  the  substance  mono-chloro-naph- 
thalene,  which  contains  73-8  per  cent.  C,  4*3  per  cent.  H,  and  21-9 
per  cent.  CI,  these  numbers  giving  the  formula  C^qH^CI.  In  the 
same  way  benzene  yields  the  compound  C^H^Cl.  In  both 
these  cases  the  halogen  acts  by  replacing  hydrogen,  and  at 
least  one  atom  of  the  latter  in  the  molecule  must  be  replaced^ 
since  fractions  of  an  atom  are  necessarily  out  of  the  question. 
If,  then,  the  compound  obtained  has  the  formula  C^oH^:Cl,  it 
follows  that  l^th  of  the  H  present  has  been  replaced  by  CI, 
and  there  must  consequently  be  8,  8  x  2,  or  8  x  3,  &c.,  atoms 
of  hydrogen  in  the  compound,  and  likewise  10  atoms,  or  some 
multiple  of  10,  of  carbon.  But  a  multiple  of  8  or  10  may  be 
rejected,  since  no  compounds  have  been  observed  which  would 


10 


INTRODUCTION. 


indicate  the  replacement  of  y^th  of  the  total  hydrogen.  This 
leads  to  the  formula  C^oHg  for  naphthalene,  the  other  possible 
formula  got  by  analysis,  viz.,  C^^Hg  (see  p.  7),  being  now 
untenable.  In  a  similar  way  the  formula  of  benzene  is  found 
to  be  CgHg. 

These  molecular  weight  determinations  by  chemical  methods 
find  their  strongest  support  in 

Determinations  of  molecular  weight  by  physical  methods. 
According  to  the  law  of  Avogadro  (1811),  and  Amjphre  (1814), 
all  gases  under  similar  conditions,  i.e,  in  the  perfectly  gaseous 
state  and  under  the  same  temperature  and  pressure,  contain  in 
equal  volumes  equal  numbers  of  molecules.  It  follows  from 
this  that  the  weights  of  equal  volumes  of  different  gases  are 
proportional  to  the  weights  of  equal  numbers  of  their  con- 
stituent molecules,  in  other  words,  the  molecular  weight  is 
proportional  to  the  specific  gravity  of  the  gas.  Thus,  if  be 
the  molecular  weight  of  any  given  substance  required,  Mh 
that  of  hydrogen,  S  the  specific  gravity  of  the  former  as  com- 
pared with  air,  and  0*06926  the  corresponding  specific  gravity 
of  the  latter,  then 

M,:Mh  =  8:0-06926. 

And  since  Mh  =  2, 

M,  =  ^^'^^  =8.28-87. 
0-06926 

To  determine,  therefore,  the  molecular  weight  of  a  gas,  one 
has  only  to  find  its  specific  gravity,  (air  =  l),  and  to  multiply 
this  by  28-87. 

To  take  an  example,  the  specific  gravity  of  acetic  acid 
vapour  being  found  to  be  2-078,  then 

M  =  2-078  X  28-87  =  60, 
and  the  molecular  formula  is  CgH^Og  =  60. 

In  like  manner,  the  specific  gravity  of  naphthalene  vapour 
is  4*33  and  the  molecular  weight  128  =  C^QHg;  the  specific 
gravity  of  benzene  vapour  2-702  and  the  molecular  weight 
78  =  CoHg. 

It  is  essential  to  the  application  of  this  method  that  the 
temperature  of  the  vapour  shall  be  so  high  above  the  boiling 


DETERMINATION  OF  VAPOUR  DENSITY. 


11 


temperature  of  the  substance  that  the  latt(^r  is  in  the  perfectly 
gaseous  state,  remaining  at  the  same  time  undecomposed. 

Another  mode  of  determining  molecular  weight  by  physical 
methods  has  been  devised  by  Raoult  (Ann.  Chem.  Phys.  1883). 
It  depends  upon  the  measurement  of  the  lowering  of  the  solidi- 
fying temperature  of  a  solvent,  e.g.  water,  benzene,  or  glacial 
acetic  acid,  which  is  produced  by  a  given  weight  of  the  sub- 
stance dissolved  ;  from  this  value,  which  is  a  function  of  the 
molecular  weight  of  the  substance  in  question,  the  latter  is 
deduced.  This  method  is  of  value,  since  it  allows  of  the 
determination  by  physical  means  of  the  molecular  weight  of 
substances  which  cannot  be  vaporized  without  decomposi- 
tion. (Cf.  V.  Meyer,  B.  21,  536;  also  B.  21,  701,  767,  860, 
E.  165,  etc.) 


Appendix:  Determination  of  the  Specific  Gravity 
of  Gases  and  Vapours.   (Vapour  Density.) 

A.  By  estimating  the  weight  of  a  given  volume  of  the  gas 
or  vapour. 

1.  Bunsen^s  method.  Three  glass  balloons  of  approximately  equal 
size  and  weight  are  used,  the  first  being  pumped  empty  of  air,  and  the 
second  and  third  filled  respectively  with  air  and  with  the  gas  in  question 
in  a  thermostat  at  a  constant  temperature.    The  respective  weights  of 

the  balloons  being  p-^^  Vz^        specific  gi;avity  = 

2.  Dumas'  method.  10  to  20  grm.  of  the  substance  are  heated  to 
boiling  in  a  round  glass  balloon  with  a  narrow  neck,  immersed,  e.g.^  in 
an  oil-bath.  After  the  temperature  has  remained  constant  for  a  con- 
siderable time,  the  point  of  the  neck  is  closed  by  the  blowpipe,  and  the 
balloon  weighed  ;  it  is  then  opened  over  mercury  and  weighed  again. 

Both  of  the  above  methods  require  a  large  quantity  of  material  and, 
further,  if  the  substance  be  not  absolutely  pure,  the  last-mentioned 
method  will  be  liable  to  the  error  caused  by  the  vapour  of  the  more 
difficultly  volatile  constituent  remaining  in  large  quantity  in  the  balloon. 
Troost  and  Hautefeuille  have  modified  the  method  for  higher  tempera- 
tures, using  a  porcelain  balloon. 

B.  By  estimating  the  volume  of  vapour  from  a  given  weight 
of  substance. 


12 


INTRODUCTION. 


1* .  Gay  Lussac's  method.  The  substance,  weighed  in  a  small  bulb, 
is  introduced  into  a  glass  cylinder  filled  with  mercury.  This  cylinder 
is  surrounded  by  a  glass  mantle,  the  lower  end  of  which  also  dips  into 
mercury,  and  which  is  filled  with  a  hot  liquid,  such  as  water,  aniline, 
etc.  The  whole  apparatus  is  warmed  and,  after  the  substance  in 
question  has  been  completely  vaporized,  its  volume  at  the  temperature 
f  is  determined. 

P.  A.  W.  Hofmann's  method.  The  substance  is  introduced 
into  a  barometer  tube  surrounded  by  a  wider  cylinder,  through 
which  the  vapour  of  a  suitable  heating  liquid  (water,  aniline, 
diphenylamine,  etc.)  is  led.  The  cylinder  can  itself  act  as  a 
reflux  condenser. 

One  advantage  of  this  method  is  that,  by  the  use  of  a  partial  or  even 
complete  vacuum,  the  boiling  point  of  the  substance  in  question  is 
lowered,  and  thus  the  vapour  density  of  compounds  which  decompose 
on  being  gasified  under  the  ordinary  atmospheric  pressure  can  be 
determined. 

2.  V.  Meyer's  air-displacement  method.  The  small  tube 
containing  the  substance  is  dropped  into  a  perpendicular  glass 
tube,  the  lower  and  wider  part  of  which  is  cylindrically  shaped 
and  sealed.  This  is  kept  warm  at  a  constant  temperature, 
being  surrounded  by  a  long  glass  mantle  in  which  a  suitable 
liquid  boils,  the  upper  part  of  the  mantle  itself  serving  for  the 
condensation  of  the  vapour.  The  displaced  air  alone  escapes, 
and  is  collected  over  water  and  measured.  No  determination, 
therefore,  of  the  temperature  of  the  vapour  of  the  substance  in 
question  is  required.  Both  of  the  above  methods  require  only 
up  to  O'l  grm.  substance.    In  all  cases 

s=? 

V 

where  g  =  the  weight  of  the  vapour,  and  v  =  the  weight  of  an 
equal  volume  of  air. 

Thus  by  the  air-displacement  method 

8=^^  ^ 


{h-w)^  273 


760     21Z  +  t  773 
where  n  —  Vae  number  of  cubic  centimetres  of  displaced  air,   1  c.c. 
of  air  weighing  -A^  of  a  gramme.     The  other  figures  have  the  same 
meaning  as  on  p.  6. 


CHEMICAL  THEORIES. 


13 


Polymerism  and  Isomerism. 

The  determination  of  molecular  weight  is  of  the  first  im- 
portance, because  different  substances  very  frequently  have  the 
same  percentage  composition  and  therefore  the  same  empirical 
analysis-formula,  and  yet  are  totally  distinct  from  one  another. 
This  difference  is  often  found  to  arise  from  difference  in  the 
size  of  the  molecule.  Thus  formic  aldehyde,  CH2O,  acetic 
acid,  C2H4O2,  lactic  acid,  CgHgOg,  and  grape  sugar,  CgH^gOo' 
have  all  the  same  percentage  composition,  as  have  also  ethy- 
lene, C2H4,  propylene,  CgH^,  and  butylene,  C^Hg.  Compounds 
standing  in  such  relation  to  each  other  are  termed  polymers. 
Very  frequently,  however,  substances  which  are  totally  dis- 
tinct from  each  other  possess  both  the  same  percentage  com- 
position and  the  same  molecular  weight ;  that  is  to  say,  these 
substances  are  made  up  not  only  of  the  same  atoms,  but  also 
of  an  equal  number  of  these  atoms  ;  such  instances  are  termed 
isomers  or  metamers.  (See  Ethers.)  Thus,  for  instance, 
common  alcohol  and  methyl  ether,  the  latter  of  which  is 
obtained  by  heating  methyl  alcohol  with  sulphuric  acid,  have 
one  and  the  same  molecular  formula,  C^Ilfi. 

The  striking  phenomenon  of  isomerism  is  only  explicable 
on  the  assumption  that  the  grouping  of  the  constituent  atoms 
of  the  molecule  is  different  in  the  two  cases.  This  difference  in 
grouping  may  be  considered  as  being  due  to  a  difference  in  the 
linking  powers  of  the  atoms,  as  is  indicated  by  the  dissimilar 
chemical  behaviour  of  isomers,  and  explained  by  the  theory  of 
valency. 

Chemical  Theories ;  the  Theory  of  Valency. 

After  the  fall  of  the  Electro-Chemical  theory,  unitary  formulae — in 
contradistinction  to  the  earlier  dualistic  formulae — were  much  used  ; 
thus  alcohol  had  the  formula  C4Hg02  (using  the  old  equivalent  weights). 
The  necessity  for  comparing  substances  of  complicated  composition  with 
simpler  ones,  taken  as  "  Types,"  had  already  repeatedly  led  to  the  pro- 
pounding of  new  theories  for  representing  the  constitution  of  organic 
compounds,  e.g.  the  older  Type  theory  (Dumas),  and  the  Nucleus 
theory  (Laurent), 


14 


INTRODUCTION. 


This  obtained  a  firmer  basis  through  Gerhar city's  Theory  of  Types, 
which  received  support  more  especially  from  the  discovery  of  the  acid 
anhydrides,  the  proper  interpretation  of  the  formulae  of  the  ethers  (see 
these),  and  the  discovery  of  ethylamine  and  other  ammonia  bases  by 
Gerhardt  (1851),  Williamson  (1850),  Hofmann  (1849  and  1850),  and 
Wurtz  (1849).  All  compounds,  inorganic  as  well  as  organic,  were  in  this 
way  compared  with  simpler  inorganic  substances  taken  as  "Types,"  of 
which  Gerhardt  named  four,  viz. — 

H 


HI 
HI 


HI 
CI  I 


N 


The  first  two  of  those  really  belong  to  the  same  type.  Thus  the  fol- 
lowing formulae,  for  example,  were  arrived  at — 

Clj  Clj  CI  / 

Potassium  chloride.    Ethyl  chloride. 


g}0  g}0  NO.}o 

Potassium  hydrate.  Nitric  acid. 

Potassium  oxide.  Nitric  anhydride. 


Alcohol. 
Ether. 


H  [^N 

hJ 


C2H5 
H 
H 


N 


CI  / 
Acetyl  chloride. 

Acetic  acid. 

Acetic  anhydride. 

C2H3O ) 

H    f  N 
H 


Ethylamine.  Acetamide. 

etc.,  etc.  Organic  compounds  could  thus,  like  inorganic,  be  referred  to 
inorganic  types  by  assuming  in  them  the  presence  of  Radicles  (e.g.  ethyl, 
C2H5 ;  acetyl,  CgHgO,  etc.),  i.e.  of  groups  of  atoms  which  play  a  role 
analogous  to  that  of  an  element,  and  which  can  be  transferred  by  double 
decomposition  from  one  compound  to  another.  Thus  ethyl  chloride, 
C2H5CI,  alcohol,  CgHgO,  ethylamine,  CgH^N,  ether,  Q^^qO,  etc.,  received 
the  same  radicle  CgHg,  ethyl,  this  showing  the  close  relationship 
existing  between  these  compounds,  a  relationship  which  now  found 
in  this  way  expression  in  writing. 

Sulphuric  acid,  H2SO4,  was  derived  from  the  double  water  type,  thus — 


and  chloroform,  CHCI3,  and  glycerin,  C3H8O; 
chloric  acid  and  water  types — 

CI3/  CI3  /  '  "3^   '  ^^3 

the  assumption  being  made  that  the  radicles  (C2H5),  (SOj)",  (CH)' 


(SO2)"  ^ 

from  the  triple  hydro- 

H3/"3  H3  |03, 


,  and 


THKORY  OF  VALENCY. 


15 


(C^Hg)"'  could  replace  a  number  of  hydrogen  atoms  corresponding  to 
the  number  of  accents  (')  marked  upon  them,  i.e.  that  they  were  mon- 
atomic,  diatomic,  etc.  To  the  above  three  types  KekuU  afterwards 
added  a  fourth,  of  especial  importance  as  regards  the  carbon  com- 
pounds, viz. — 


It  was  then  found  that  many  compounds  could  be  referred  equally  well 
to  one  or  another  of  these  types,  methylamine,  for  instance,  either  to  CH4 
or  to  NHq,  thus — 


The  assumption,  already  mentioned,  of  the  atomic  groups  (radicles) 
which  in  these  types  replaced  hydrogen,  led  further  to  more  exact 
investigations  of  the  chemical  value,  i.e.  the  replaceable  value,  of  those 
groups  as  compared  with  that  of  hydrogen.  In  this  way  one  learnt  to 
distinguish  between  mono-,  di-,  tri-,  etc.,  valent  groups,  and,  generally 
speaking,  to  pay  more  attention  to  equivalent  proportions.  Out  of  this 
there  grew  the  conviction  that  a  more  profound  idea  (the  '  *  Type  idea  ") 
lay  at  the  root  of  the  types  themselves — viz.,  that  there  are  mono-, 
di-,  tri-,  and  tetra valent,  etc.,  elements,  which  possess  a  corresponding 
replacing  or  combining  value  as  regards  hydrogen  {Kekul4,  1857  and 
1858,  A.  104,  129,  and  106,  129),  and  that  therefore  H  is  monovalent, 
0  divalent,  N  trivalent,  C  tetravalent,  and  so  on. 

The  principles  of  the  theory  of  Valency  or  theory  of  Chemical  Values 
are  in  this  book  assumed  to  have  been  already  learnt  from  inorganic 
chemistry. 

With  the  setting  up  of  the  type  CH4  by  KekuU,  and  the  knowledge  of 
the  tetravalent  nature  of  carbon  accompanying  this,  were  connected  the 
endeavours  of  Kolbe  to  derive  the  constitution  of  organic  compounds 
from  carbonic  acid,  (according  to  Kolbe  C2O4,  C=6,  0  =  8),  but  from  an 
incomplete  grasp  of  the  subject  of  equivalent  proportions  a  clear  insight 
into  this  was  not  arrived  at.     (See  note  on  page  xix. ) 

The  question  of  the  valency  of  elements,  a  point  which  it  is 
often  difficult  to  decide  in  inorganic  chemistry,  is  infinitely 
easier  of  determination  in  the  case  of  the  carbon  compounds, 
because  carbon  shows  itself  tetravalent  towards  hydrogen  as 
well  as  towards  chlorine  and  oxygen.  Since  now  hydrogen  as 
the  unit  of  valency  is  monovalent,  and,  further,  since  the 
divalence  of  oxygen  cannot  reasonably  be  doubted,  the  valency 


16 


INTRODUCTION. 


of  the  three  "  organic  "  elements  H,  0,  and  C  may  be  considered 
as  resting  upon  a  sure  basis,  as  may  also  the  conclusions  drawn 
therefrom,  and  this  all  the  more  since  the  most  important 
carbon  compounds  are  made  up  of  those  three  elements. 


Explanation  of  Isomerism  ;  Determination  of  the 
Constitution  of  Organic  Compounds. 

The  theory  of  valency  makes  the  phenomenon  of  Isomerism 
easy  to  understand.  That  this  depends  upon  the  different 
grouping  or  combination  of  the  atoms  in  the  molecule  follows 
from  the  fact  that  isomeric  bodies,  upon  chemical  transforma- 
tion, break  up  into  or  exchange  perfectly  different  atomic 
groups  or  atoms. 

We  now  arrive  at  the  task  of  determining  the  different  modes 
of  combination  of  the  atoms  in  the  molecule,  i.e.,  the  chemical 
constitution  of  the  carbon  compounds. 

This  is  in  every  case  only  possible  and  permissible  for  com- 
pounds whose  chemical  behaviour  in  the  most  dissimilar 
directions  is  known. 

The  points  of  view  which  determine  this  can  best  be 
explained  by  giving  an  example.  When  an  ethereal  solution 
of  methyl  iodide,  CH3I,  is  treated  with  sodium,  there  is  first 
formed  the  group  CHg,  methyl,  which — from  carbon  being 
tetravalent — must  have  a  "  free  affinity (^) — 

\H 

The  determination  of  the  molecular  weight  of  the  gaseous 
compound  ethane,  formerly  called  methyl,  which  is  thus  pro- 
duced, shows  however  that  it  has  the  formula  C^B.^^^^  ^C^Hg). 
The  two  methyl  groups  have  therefore  combined  together,  and 
it  cannot  well  be  doubted  that  this  combination  is  effected  by 
their  free  affinities.  Ethane  therefore  receives  the  constitu- 
tional formula — 

C=H3 
H3C— CH3;=  I  j 
C=H, 


DETERMINATION  OF  CONSTITUTION. 


17 


or,  more  shortly, 

CH3  /CH3\ 

This  ethane  can  also  be  prepared  from  common  alcohol.  By  the 
action  of  a  halogen-hydride  upon  alcohol,  one  atom  of  oxygen 
and  one  of  hydrogen  together  are  exchanged  for  an  atom  of 
the  halogen  with  formation,  for  example,  of  C^H^Cl,  ethyl 
chloride ;  then  nascent  hydrogen,  acting  upon  this  chloride, 
replaces  the  halogen,  thus, 

C^HgO  +  HCl  =  C2H5CI  +  H2O  ; 

C2H5C1  +  H2  =  C2H,  +  HC1. 
Conversely,  by  treating  ethane  with  chlorine,  ethyl  chloride, 
C2H5CI,  can  be  formed,  and  from  this  latter  compound, 
alcohol.  (See  Special  Part.)  Thus,  one  atom  of  oxygen  and 
one  of  hydrogen  have  here  replaced  one  atom  of  chlorine, 
from  which  it  follows  that  the  two  first-named  together  form 
the  monovalent  residue — (0 — H),  hydroxyl.  It  is  also 
evident  from  this  reaction  that  one  atom  of  hydrogen  in 
alcohol  behaves  differently  to  the  other  five,  and  must  con- 
sequently be  difi*erently  bound.  Thus  it  is,  for  instance,  re- 
placeable by  metals,  acid  radicles,  etc.,  and,  when  the  oxygen 
is  removed  from  the  compound,  it  is  removed  also,  whereas 
the  other  five  hydrogen  atoms  are  not  affected.  It  is 
especially  to  be  noted  that  the  relation  of  the  two  carbon 
atoms  to  one  another  is  not  altered  by  the  removal  of  the 
oxygen. 

All  these  facts  lead  to  the  constitutional  formula  for  alcohol : 

CHo— CH2OH  or  /H. 

C— H 
\0— H 

In  methyl  ether,  C2HgO,  which  is  isomeric  with  this  alcohol, 
no  one  of  the  six  hydrogen  atoms  shows  any  difference  to  the 
others ;  and,  further,  when  its  oxygen  is  removed,  say  by  the 
action  of  hydriodic  acid,  the  connection  between  its  two  carbon 
atoms  is  broken,  with  the  formation  of  products  which  contain 

(506)  B 


18 


INTRODUCTION. 


only  one  atom  of  carbon  in  the  molecule,  these  products  being, 
according  to  the  conditions, — either  one  molecule  methyl  iodide 
and  one  molecule  methyl  alcohol  or  two  molecules  methyl 
iodide,  thus — 

CgHgO  +  HI  =  CH4O  +  CH3I, 
or,  O^HgO  +  2HI  -  2OH3I  +  H^O. 

From  this  it  is  to  be  concluded  that  in  methyl  ether  the  two 
carbon  atoms  are  not  bound  directly  to  one  another,  but  only 
by  interposition  of  the  oxygen.  These  conditions  find  expres- 
sion in  the  following  constitutional  formula — 

C=H3 
I 

CH3— 0— CH3  ;  or  0 

C^H3 

In  a  precisely  analogous  manner  we  obtain  for  acetic  acid  the 
constitutional  formula — 

H    ,  O 


i^OH;  or  H- 


-U- 
i- 


H    0— H 

On  account  of  the  innumerable  cases  of  isomerism  which 
have  been  observed,  empirical  formulae  alone  are  in  most  cases 
insufficient  for  the  discrimination  of  organic  compounds  ;  it 
generally  requires  the  constitutional  formulae  to  give  a  clear 
idea  of  their  behaviour  and  of  their  relations  to  other  sub- 
stances. Careful  study  has  made  it  possible  within  the  last 
few  decenniums  to  find  out  the  mode  in  which  the  atoms  are 
combined  in  the  molecule  of  most  organic  compounds,  and 
from  this  to  deduce  new  methods  for  their  preparation. 

The  theoretical  views  and  the  knowledge  thereby  gained  of 
the  nature  of  carbon  may  be  expressed  somewhat  as  follows — 

1.  Carbon  is  tetravalent. 

2.  Its  four  valencies  are  all  equal ;  there  is  only  one  mono- 
substitution  product  of  methane. 

3.  The  atoms  or  atomic  groups  which  are  held  bound  by 
thetie  four  valencies  cannot  directly  exchange  places  with 


RATIONAL  FORMULAE. 


19 


each  other.  Proof:  there  are  in  every  case  two  physically 
different  tetra-substitution  products  C,  a,  b,  c,  d  of  methane 
(see  p.  23). 

4.  Several  carbon  atoms  can  be  connected  together  by  either 
one,  two,  or  three  valencies. 

5.  Those  compounds  form  either  open  or  ring-shaped  closed 
chains. 

One  may  picture  the  carbon  atom  in  one's  own  mind  as  a  tetrahedron, 
the  four  corners  of  which  represent  the  affinities  or  affinity -directions, 
and  which  is  regular  if  the  carbon  atom  is  combined  with  four  atoms 
similar  to  each  other,  but  of  less  symmetrical  form  in  other  cases.  One 
has  thus  to  think  of  two  carbon  atoms,  connected  by  a  single  bond,  as 
colliding  at  an  angle  of  the  tetrahedron,  but  free  to  move  round  each 
other ;  of  two  carbon  atoms,  connected  by  a  double  bond,  as  joined 
together  at  an  edge  of  the  tetrahedron,  but  no  longer  free  to  revolve 
round  each  other;  and  of  two  carbon  atoms,  connected  by  a  triple  bond, 
as  joined  by  two  sides  of  the  two  tetrahedrons. 

Such  conceptions  have  proved  of  great  value  in  the  investigation  of 
the  finer  cases  of  isomerism,  on  the  one  hand,  as  regards  the  optical 
dififerences  of  substances  which  are  chemically  identical,  (e.  g.  the  lactic 
and  the  tartaric  acids),  and  on  the  other  as  regards  many  differences, 
hitherto  unexplained,  between  bodies  which  appear  to  possess  the  same 
chemical  constitution,  especially  such  as  contain  a  double  carbon  bond 
in  the  molecule,  {e.g.  fumaric  and  maleic  acids,  p.  218).  (Cf.  Van 
H  Hoff,  "Dix  Annies  dans  I'histoire  d'une  theorie,"  Rotterdam,  1887  ; 

Wislicenus,  "  Raumliche  Anordnung  der  Atome,  etc,"  Leipzig  (Hirzel)^ 
1887,  referred  to  in  B.  20,  R.  448 ;  Baeyer,  B.  18,  2277  ;  A.  245,  103  ; 

V.  Meyer,  B.  21,  784,  946). 

Rational  Formulae. 

Great  latitude  is  permissible  as  regards  the  mode  of  writing 
constitutional  formulae,  according  to  the  particular  points 
which  it  is  desired  to  emphasize.  The  symmetrical  arrange- 
ment or  otherwise  of  the  formula  on  paper  is  of  no  consequence, 
because  the  prevailing  theories  have  regard  almost  alone  to 
the  mode  of  combination,  and  not  to  the  actual  positions  of 
the  atoms.  Upon  this  latter  point,  experiment  can  yield 
almost  no  data. 

A  shortened  constitutional  formula,  which  indicates  more 
chemical  relations  than  an  empirical  one  does,  is  called  a 
rational  formula;  g.^.,  CgH^OH,  alcohol;  (0113)20,  methyl  ether. 


20 


INTRODUCTION. 


For  acetic  acid,  instead  of  the  constitutional  formula  already 
given  on  page  18,  the  following  rational  formula  may  be 
used — ■ 

CH3— C<Qjj    CH3— CO.OH,  CH3— CO2H,  CH3.CO2H, 
(CH3.CO)6h,    C2II3O.OH,    H(C2H302),  and  so  on. 


Homology. 

On  replacing  the  hydrogen  in  methane  by  1,  2,  3,  or  4 
atoms  of  chlorine,  the  substitution  products,  CH3CI,  CH2CI2, 
CHCI3,  and  CCI4  result.  The  halogen  in  these  can,  in  its  turn, 
be  replaced  by  oxygen  (CI  by  OH,  201  by  0,  and  301  by  0 
and  OH  together) ;  in  this  way  we  obtain  the  following  com- 
pounds— 

OH3OH.  CH2O.  OHO.  OH  or  CH2O2. 

Methyl  alcohol.   Formic  aldehyde.         Formic  acid. 

From  ethane,  C2Hg,  which  so  closely  resembles  methane, 
similar  compounds  are  derivable,  compounds  which,  in  their 
chemical  properties,  are  in  every  respect  analogous  to  those 
from  methane,  but  differ  from  them  in  composition  by  the 
addition  of  CH2. 

The  same  holds  good  for  compounds  with  three  and  more 
carbon  atoms.  Thus,  corresponding  to  methane  and  ethane, 
we  have  propane,  C3Hg,  butane,  O^H^q,  etc.  ;  to  methyl  alcohol 
and  ethyl  alcohol,  propyl  alcohol,  C3H^.0H,  and  so  on. 

Substances  which  differ  from  each  other  in  composition  by 
a  constant  quantity  such  as  CH2  or  some  multiple  of  CH2,  and 
which  at  the  same  time  resemble  each  other  closely  in  their 
chemical  behaviour,  are  termed  homologous,  and  can  be 
arranged  in  "  homologous  series,"  thus — 


OH, 
Methane. 


CgHg 

Ethane. 


CH3CI 
Methyl 
chloride. 

C2H,C1 
Ethyl 
chloride. 


CH3.OH 
Methyl 
alcohol. 

C2H5.OH 
Ethyl 
alcohol. 


Formic 
aldehyde. 

C,H,0 
Acetic 
aldehyde. 


Formic  acid. 


C2H4O2 
Acetic  acid. 


HOMOLOGY. 


21 


Propane. 


Butane. 


C,H,C1 
Propyl 

Propionic 

Propyl 

chloride. 

alcohol. 

aldehyde. 

C^H.Cl 

Butyl 

C.HeO 
Butyric 

Butyl 

chloride. 

alcohol. 

aldehyde. 

Propionic 
acid. 

C4H8O2 
Butyric 
acid. 


The  following  general  formulae  can  also  be  given  for  these 
series — 

Homology  constitutes  a  most  important  aid  in  the  study  of 
organic  chemistry,  because  the  compounds  belonging  to  a 
homologous  series  nearly  always  show  analogous  properties, 
and  thus  the  study  of  a  single  member  often  suffices  for  the 
whole  group. 

From  a  physical  point  of  view,  it  is  observable  that,  with  an 
increase  in  the  number  of  carbon  atoms,  the  tendency  of  the 
compounds  is  to  change  gradually  from  the  gaseous  to  the 
liquid  or  solid  state.  Thus,  the  compound  CgHg  is  gaseous, 
6511^2  is  liquid  at  the  ordinary  temperature,  C1QH22  also  liquid, 
but  with  a  rather  high  boiling  point  (173°),  while  C20H42  is 
solid,  boiling  only  above  300°.  Similarly,  formic  acid  is 
liquid,  and  the  corresponding  acid  with  16  atoms  of  carbon 
solid  ;  the  former  boils  at  99°,  the  latter  at  over  300°. 

But  more  lies  in  homology.  All  the  homologues  of  methane, 
CH4,  contain  the  maximum  number  of  hydrogen  atoms  which 
can  be  taken  up  by  the  number  of  carbon  atoms  in  question, 
viz.,  2ni-2  atoms  of  hydrogen  for  n  atoms  of  carbon  ;  under 
no  circumstances  can  more  hydrogen  than  this  be  bound. 

Just  as  ethane  can  be  derived  from  methane  by  substituting 
for  H  the  monovalent  group  CH3,  the  composition-difference 
CH2  following  as  a  consequence  of  the  tetravalence  of  carbon, 
so  are  all  the  higher  hydrocarbons  of  this  series  derived  from 
those  poorer  in  carbon  by  the  continuous  exchange  of  H  for 


CH3 ;   thus  the  formula  of 


CH4  +  (7i  +  l).CH2,  i.e.  G,,U,, 


all  the  higher  homologues  is 
The  tetravalence  of  carbon  is 


therefore  manifestly  the  cause  of  the  homology. 

The  grouping  together  of  the  carbon  atoms  must  thus  be 


22 


INTRODUCTION. 


conditioned  by  themselves,  since  hydrogen,  as  a  monovalent 
element,  cannot  be  the  cause  of  it.  In  all  the  higher  hydro- 
carbons, the  carbon  atoms  are  therefore  combined  together  in 
the  form  of  a  chain,  as  it  were,  as  the  following  graphical 
representation  shows  : 

C  0 

0,  C,     C— C— C— C,  or  C— C;  and  so  on. 

I  I  I 

c        c  c 

in  CgHg.     in  GJl^.  in  G^E.-^q. 

Various  cases  can  occur  in  the  mode  of  combination  of  the 
carbon  atoms  (Isomers).  (See  Hydrocarbons  of  the  Methane 
Series.) 

Law  of  Even  Numbers  of  Atoms. 

The  number  of  hydrogen  atoms  in  the  above  hydrocarbons  is  always 
divisible  by  two.  Should  they  therefore  be  partially  replaced  by  other 
elements,  the  sum  of  these  latter,  if  their  valencies  are  expressed  by 
odd  numbers,  e.g.  CI,  N,  and  P,  and  of  the  remaining  hydrogen  atoms 
taken  together  must,  as  a  necessary  consequence  of  the  law  of  equivalent 
proportions,  remain  an  even  number. 


Radicles. 

According  to  Liehig,  radicles  were  groups  of  atoms  capable 
of  a  separate  existence,  which  played  the  parts  of  elements, 
and,  like  these  latter,  could  combine  among  themselves  and 
be  exchanged  from  one  compound  to  another. 

Later  on,  the  postulate  that  such  radicles  must  also  be 
capable  of  existing  in  the  free  state  was  allowed  to  lapse,  and 
they  were  frequently  defined  shortly  as  "  the  residues  left 
unattacked  by  certain  decompositions.^' 

Now,  however,  it  is  usual  to  designate  as  radicles  only  those 
atomic  groups  which  are  found  repeating  themselves  in  a  com- 
paratively large  number  of  compounds  derived  from  one  another, 
and  which  play  in  these  compounds  the  role  of  a  simple 
element,  e.g.  CHg,  methyl,  CgHgO,  acetyl ;  by  this  definition 
the  question  of  their  capability  of  existence  when  isolated  does 


CLASSIFICATION  OK  TlIK  HYDROCARliONS. 


23 


not  come  np.  The  radicle  methyl,  for  exam})le,  is  not  known 
in  the  free  state,  since,  when  its  formation  might  be  expected, 
ethane  (di  methyl),  CH3 — CH3,  is  obtained  instead  (see  pages 
16  and  17).  Such  radicles  may  be  mono-,  di-,  or  tri-valent,  etc., 
according  to  the  number  of  monovalent  atoms  which  they  are 
capable  either  of  replacing  or  of  combining  with,  so  as  to  form 
a  saturated  compound  ;  for  instance,  (CgH^)'',  ethylene,  is 
divalent ;  (C3H5)''',  glyceryl,  trivalent ;  (CH)''',  methine  or 
methenyl,  likewise  trivalent,  etc. 

Classification  of  the  Hydrocarbons,  etc. 

The  hydrocarbons  which  have  already  been  described  are 
termed  "  saturated "  compounds,  since  they  cannot  take  up 
more  hydrogen.  But  besides  these  there  are  hydrocarbons,  etc., 
poorer  in  hydrogen,  or  "unsaturated,"  such  as  CgH^,  ethylene, 
and  C2H2,  acetylene,  corresponding  to  which  there  are  like- 
wise homologous  series. 

The  constitution  of  these  is  explained,  as  will  be  seen  later, 
by  the  assumption  of  a  double  or  triple  bond  between  neigh- 
bouring carbon  atoms,  for  instance — 


From  these  different  hydrocarbons,  as  starting  points,  the 
most  various  substitution  products,  such  as  alcohols,  aldehydes, 
ketones,  acids,  etc.  (see  p.  20),  are  derived  by  exchange  of  the 
hydrogen  for  halogen,  oxygen,  nitrogen,  etc. 

To  another  class  of  hydrocarbons  belongs  that  most  import- 
ant compound  benzene,  CgHg,  which  contains  eight  atoms  of 
hydrogen  less  than  hexane,  CgH^^.  With  regard  to  its  con- 
stitution, the  theory  of  the  existence  of  a  closed  chain  of  six 
carbon  atoms  has  been  advanced.  (See  Benzene  Derivatives). 
From  benzene  are  derived  an  immense  number  of  the  most 
different  homologous  and  analogous  hydrocarbons  and  sub- 
stitution products,  alcohols,  aldehydes,  acids,  and  so  on. 
Thus  benzene,  like  methane,  is  the  mother  substance  of 


CH 

in' 


24 


INTRODUCTION. 


numerous  organic  compounds.  The  same  holds  good  for  the 
base  pyridine,  C^H^N,  which,  while  containing  nitrogen, 
resembles  benzene  in  many  points.  Organic  chemistry  is 
therefore  divided  into  the  two  following  large  sections  : 

1.  Chemistry  of  the  Methane  Derivatives,  or  Chemistry  of 
the  Fatty  Compounds,  (so  called  because  the  fats  and  many 
compounds  derivable  from  them  belong  to  this  group). 

2.  Chemistry  of  the  Benzene  Derivatives,  or  Chemistry  of 
the  Aromatic  Compounds ;  this  is  followed  by  the  chemistry 
of  the  pyridine  derivatives  (chiefly  alkaloids). 

Physical  Properties  of  Organic  Compounds. 

The  physical  properties  of  organic  compounds  are  often  of 
the  greatest  importance  for  their  characterization.  They  fre- 
quently show  a  more  or  less  regular  relation  to  the  composition 
and  constitution  of  the  compounds.  A  few  of  these  may  be 
mentioned  here. 

Colour. 

Most  organic  compounds  are  colourless  ;  compounds  con- 
taining iodine  and  nitro-compounds  are  frequently  yellow  or 
red.  Many  substances  are  converted  into  dyes  by  the  entrance 
of  the  salt-forming  groups  NHg  or  OH;  for  instance,  tri-phenyl- 
carbinol,  thio-diphenylamine,  and  azo-benzene  (see  these);  those 
substances  are  termed     chromogenes."    {Witt,  B.  9,  522.) 

Solubility, 

The  hydrocarbons  and  their  substitution  products  are  either 
insoluble,  or  only  slightly  soluble  in  water.  While  the  lower 
members  of  a  homologous  series  of  the  alcohols,  such  as  methyl 
and  ethyl  alcohols  and  glj^cerine,  dissolve  for  the  most  part 
easily  in  water,  the  higher  homologues  are  either  difficultly 
soluble  or  insoluble.  The  polyatomic  (polyhydric)  alcohols, 
e.g.  mannite,  are  readily  soluble  in  water,  but  unlike  the 
monatomic,  are  mostly  insoluble  in  ether.  Aldehydes, 
ketones,  and  acids  behave  similarly  to  alcohols.    The  benzene 


PHYSICAL  PROPERTIES. 


25 


derivatives  are,  as  a  rule,  less  soluble  in  water  and  alcohol 
than  the  analogous  fatty  compounds. 

Most  organic  compounds  dissolve  in  alcohol,  and  the  greater 
proportion  in  ether. 

Specific  Gravity  and  Molecular  Volume. 

The  specific  gravities  of  isomeric  compounds  are  different. 
Those  of  the  normal  hydrocarbons,  determined  at  their  melting 
points,  approach — with  increase  of  carbon — to  a  definite  limit 
(about  0'78),  which  is  already  almost  reached  in  the  case  of 
CjgHg^.    (See  the  Paraffins.) 

The  specific  gravities  of  the  normal  hydrocarbons,  GJ^^n  and 
C^Hgn-oj  from  C^g  onwards,  likewise  approach  this  limit,  but 
more  slowly  and  in  a  downward  direction ;  thus,  C^gllgg  has 
the  specific  gravity  0-791,  and  CigHg^  that  of  0-802.  The 
specific  gravities  of  the  monobasic  fatty  acids,  beginning  at  a 
number  greater  than  1,  also  sink  with  increasing  carbon  and 
approach  to  the  above-mentioned  limit,  only  very  much  more 
slowly  than  in  the  case  of  the  hydrocarbons. 

The  Molecular  Volume,  sometimes  also  termed  the  Specific  Volume, 
is  the  quotient  from  the  molecular  weight  and  the  specific  gravity. 

Schroder  has  calculated  various  laws  for  the  molecular  volume  of  solid 
bodies,  but  they  cannot  be  depended  upon.  In  the  acetic  acid  homo- 
logous series  the  molecular  volume  increases  in  the  silver  salts  by  about 
15-8  for  every  increment  of  CHg.    (See  B.  lO,  848,  1871  ;  14,  2516.) 

By  comparing  the  molecular  volumes  of  liquids  under  similar 
conditions,  ix.  at  their  boiling  temperatures,  H.  Kop^p  a  long 
time  ago,  and  with  the  material  then  available,  observed 
certain  approximate  relations,  which  allowed  of  expression  in 
these  words  :  the  molecular  volume  of  a  compound  is  equal  to 
the  sum  of  the  atomic  volumes  of  its  constituent  elements. 
(A.  46,  212;  92,  1;  94,  269:  96,  171,  etc.)  Thus,  in 
homologous  series  an  increase  of  about  22  was  observed  for 
each  CH2,  and  in  this  way  it  appeared  possible  to  deduce  from 
the  molecular  volume  of  compounds  the  atomic  volumes  of  their 
constituent  elements.  For  carbon  this  was  found  to  be  11, 
and  for  hydrogen  5-5.  For  the  polyvalent  elements,  especially 
for  oxygen  and  nitrogen,  varying  values  were  obtained  by 


26 


INTRODUCTION. 


calculation,  the  value  appearing  to  depend  upon  the  mode  in 
which  the  elements  were  combined.  Thus,  the  O  which  was 
joined  to  C  by  a  double  bond  in  a  compound  had  the  volume 
7*8,  while  that  joined  by  a  single  one  had  the  volume  12*2. 

Later  investigations,  which  have  had  much  more  material  to 
work  upon  in  consequence  of  recent  discoveries,  have  shown 
that  the  above  law  is  only  approximately  true.  Thus  isomeric 
bodies  have  not  the  same,  but  somewhat  different  molecular 
volumes.  In  unsaturated  compounds  each  double  bond  of 
C  to  C  appears  to  increase  the  molecular  volume.  Even  when 
their  atoms  are  similarly  combined,  isomeric  bodies  have 
different  molecular  volumes :  for  example,  ethylene  chloride 
and  ethylidene  chloride,  whose  molecular  volumes  differ  by 
4  per  cent,  of  their  value.  (Cf.  Thorpe,  Ch.  Soc.  J.  37,  141  ; 
Lossen  and  his  Pupils,  A.  211,  214,  and  221;  ScUff,  A.  220,  71 ; 
Staedel,  B.  15,  2559 ;  Horstmann,  B.  19,  1579 ;  BrUhl,  A.  235, 
1,  and  others.) 

Recent  investigations  by  Horstmann  (B.  20,  766)  have  shown  that  in 
the  case  of  compounds  of  the  benzene  and  pyridine  series,  in  which  one 
assumes  a  closed  carbon  chain  (p,  311),  the  molecular  volume  is  dis- 
tinctly less  than  in  the  case  of  isomers  containing  two  carbon  atoms 
joined  together  by  a  double  bond  (p.  49).  The  same  law  holds  good  for 
pyrrol  and  thiophene  derivatives.    (Cf.  Ladenhurg,  B.  21,  292.) 

Laws  regulating  the  Boiling  Point. 

1.  In  homologous  compounds  the  boiling  point  rises,  in  the 
case  of  substances  of  analogous  constitution,  by  an  increment 
for  each  CHg  which  is  constant  in  the  lower  members  of  the 
series;  this  is  19°-20°  for  each  CHg  in  the  lower  members  of 
the  methyl  alcohol  and  formic  acid  series,  and  30°  in  the  series 
of  the  methylated  benzenes  (containing  the  methyl  group  in 
the  benzene  ring).  In  the  higher  members  of  a  series,  i.e. 
with  increasing  carbon,  the  temperature-difference  decreases. 
(See,  as  an  example,  the  Methane  Series.) 

2.  The  boiling  points  of  the  normal  hydrocarbons  of  the 
series  C^Hgn+ai  CnHan,  and  GJl2n^'i  9,re  very  near  to  each 
other;  e.g,  CigHgs,  181  -5,  G^^H^^,  179^  and  CigHg^,  184*. 


BOILING  POINT;    FRACTIONAL  DISTILLATION.  27 

3.  In  the  case  of  isomeric  substances,  tlie  noiiual  compound 
in  the  fatty  series  has  the  highest  boiling  point ;  the  more 
branching  the  C-chain  is,  the  lower  is  the  boiling  point.  (See 
the  Hydrocarbons  Grjii2  ^^^d  the  Acids  Cr^ll-^QO^-) 

4.  The  entrance  of  halogens  generally  raises  the  boiling 
point  considerably,  the  first  Cl-atom,  for  instance,  by  about 
60°,  and  the  succeeding  ones  by  a  less  amount.  (See,  e.g., 
Chlorinated  Methanes  and  Acetic  Acids.) 

5.  On  comparing  compounds  which  contain  hydroxy!  with 
the  substances  from  which  they  are  derived,  it  is  seen  that  the 
entrance  of  the  OH  group  has  caused  a  considerable  rise  in 
the  boiling  point ;  and,  further,  that  while  the  mother  sub- 
stance may  distil  unchanged,  the  hydroxyl  derivative  frequently 
decomposes  upon  distillation.  Thus,  propionic  acid  is  volatile, 
while  lactic  acid  (oxy-propionic)  is  not. 

6.  The  boiUng  points  of  ethers  (see  these)  are  considerably  lower  than 
those  of  the  isomeric  alcohols,  or  even  of  the  corresponding  alcohols ; 
thus,  ethyl  ether  boils  at  35°,  the  isomeric  butyl  alcohol  at  117°,  and 
ethyl  alcohol  at  78°.  The  same  thing  applies  to  the  compounds  derived 
from  the  alcohols  by  exchange  of  OH  for  SH  or  NH2,  (mercaptan, 
C2H5SH,  boils  at  36°  ;  ethylamine,  C2H5NH2,  at  18°)"^;  and  to  the 
glycols  and  their  simple  ethers,  (glycol  boils  at  197°,  ethylene  oxide 
at  13°). 

7.  Aromatic  ortho-  di- derivatives  are  more  easily  volatilized  than 
the  isomeric  para-derivatives,  etc.,  etc. 

Fractional  Distillation. 

The  separation  by  distillation  of  two  substances  which  boil 
at  different  temperatures  can  only  be  carried  out  easily  when 
the  interval  between  the  boiling  points  is  a  large  one.  If 
these  only  differ  from  one  another  slightly,  say  by  10°-30°, 
the  tension  of  the  vapour  of  the  higher  boiling  liquid  is  already 
so  considerable  at  the  temperature  at  which  the  lower  one 
boils,  that  it  partly  distils  over  with  the  latter.  As  a  conse- 
quence, one  observes  in  such  cases  a  continuous  rise  of  the 
thermometer  without  its  remaining  stationary  at  any  given 
boiling  point,  and  a  gradual  (not  intermittent)  change  in  the 
composition  of  the  distillate. 


28  INTRODUCTION. 

In  such  cases  one  must  distil  fractionally/*  i.e.  the  dis- 
tillate must  be  collected  in  separate  "fractions,"  according  to 
the  rise  of  boiling  point,  e.g..  from  5°  to  5",  and  each  of  these 
fractions  must  be  again  fractionated  by  itself.  The  operation 
has  to  be  repeated  until  the  middle  fractions  have  been 
separated  into  the  higher  and  lower  boiling  constituents,  i.e. 
until  the  separation  of  these  latter  has  been  effected.  To 
facilitate  the  operation,  apparatus  is  used  which  favours  a 
partial  condensation  of  the  vapour,  by  which  means  the 
vapour  of  the  higher  boiling  substance  is  mostly  liquefied ; 
(fractionating  apparatus  by  Wurtz,  Linnemann,  Glinsky,  Hennin- 
ger,  Le  Bel,  Hempel,  JVarren).  On  the  large  scale,  apparatus 
depending  upon  the  same  principle  and  called  "  column 
apparatus  "  and  "  dephlegmators,''  are  employed  for  separating 
the  benzene  hydrocarbons  and  for  purifying  alcohol. 

Even  with  liquids  whose  boiling  points  are  relatively  wide  apart  from 
one  another,  cases  ma.y  arise  in  which  a  separation  by  fractional  distilla- 
tion is  difficult  or  even  impossible.  As  an  example  of  the  latter,  it 
may  be  mentioned  that  a  mixture  of  2  volumes  water  with  3  volumes 
amyl  alcohol  (B.  Pt.  135°)  boils  at  the  constant  temperature  of  96°, 
and  a  similar  mixture  of  carbon  bisulphide  and  water  at  43° ;  from  a 
mixture  of  aniline  and  water,  the  former  distils  more  quickly  than  the 
latter,  although  its  boiling  temperature  is  80°  higher. 

When  two  substances  which  do  not  mix  with  one  another,  or  whose 
vapour  tensions  are  not  altered  upon  mixing,  are  distilled  together,  the 
quantity  of  each  which  passes  over  is  proportional  to  the  product  of  the 
vapour  tension  at  the  boiling  temperature  of  the  mixture  into  the 
vapour  density.  (G  :  g  =  MP  :  mp,  where  m.  is  the  molecular  weight,  g. 
the  weight  in  the  distillate,  and  p.  the  vapour  tension  of  the  one  con- 
stituent at  the  boiling  temperature  of  the  mixture,  M.G.P.  being  the 
corresponding  values  for  the  other  constituent.  WanUyii's  law,  corro- 
borated by  Berthelot  and  Tliorpe. )  Since  the  molecular  weight  is  pro- 
portional to  the  specific  gravity,  it  is  possible  to  calculate  by  this  law 
the  molecular  weight  of  a  substance  from  the  observed  proportions  in 
which  two  constituents  of  a  mixture  distil,  provided  the  molecular 
weight  of  the  other,  e.g.,  water,  is  known,  {Naumann). 

Laivs  Regulating  the  Melting  Point. 

1.  One  frequently  observes  in  homologous  series  that  the  melting 
points  of  the  successive  members  alternately  rise  and  fall  in  such  a 
manner  that  the  members  with  an  odd  number  of  carbon  atoms  have  a 


HEAT  OF  NEUTRALIZATION. 


29 


lower  melting  point  than  those  containing  an  atom  of  carbon  less,  while 
the  melting  points  of  the  members,  both  with  odd  and  with  even 
numbers  of  carbon  atoms,  when  regarded  alone,  rise  regularly  (formic 
acid  series),  or  also  in  part  fall  (succinic  acid  series). 

2.  Of  the  isomeric  di-derivatives  of  benzene,  the  /^-compounds  have 
the  highest  melting  point,  and  are  often  solid  when  the  m-  and  o-com- 
pounds  are  still  liquid.  The  lengthening  out  of  the  side  chains  causes 
a  lowering  of  the  melting  point. 

3.  In  compound  ethers,  the  methyl  ethers  have  frequently  a  higher 
melting  point  than  the  ethyl,  and  the  ethyl  a  higher  one  than  the 
propyl,  etc. ;  thus  the  methyl  ether  of  oxalic  acid  is  solid,  and  the  ethyl 
ether  liquid. 

4.  The  melting  point  of  a  mixture  of  two  substances  alters 
with  its  composition  in  this  way,  that,  with  a  definite  composi- 
tion, a  minimum  of  melting  point  is  attained,  which  lies  below 
that  of  the  lower  melting  constituent.  As  examples  of  this 
may  be  mentioned  a  mixture  of  stearic  and  palmitic  acids, 
which,  on  account  of  its  lower  melting  point,  was  for  long  held 
to  be  a  separate  acid,  margaric  acid";  or  a  mixture  in  equal 
proportions  of  para-  and  meta-oxybenzoic  acids,  which  melts 
at  143°-152°,  while  the  acids  separately  melt  respectively  at 
210°  and  290^ 

Even  very  small  quantities  of  admixtures  may  materially 
reduce  the  melting  point  of  a  compound.  The  constancy  of  the 
melting  point  of  a  substance  after  repeated  recrystallizations  is 
therefore  a  valuable  criterion  of  its  purity. 

Heat  of  Neutralization, 

The  value  of  the  heat  of  neutralization  of  organic  acids  in 
aqueous  solution  by  caustic  soda  is  approximately  the  same  for 
the  organic  carboxylic  acids,  i.e,  for  those  which  contain  the 
radicle  carboxyl,  COOH,  in  so  far  as  their  salts  are  not  decom- 
posed by  water,  being  as  a  rule  somewhat  over  12,000  calori- 
metric  units.  Phenols  give  only  about  half  this  value,  while 
for  ordinary  alcohols  under  similar  conditions  it  is  very  small. 
Use  can  be  made  of  this  to  determine  the  function  of  the  hydroxy  1 
in  any  compound.  The  entrance  of  a  negative  radicle,  such  as 
NOg,  into  a  phenol,  which  converts  it  into  an  actual  acid,  is  also 
accompanied  by  a  rise  in  the  heat  of  neutralization,  (Berthelot) 


30 


INTRODUCTION. 


Heat  of  Combustion  and  Heat  of  Formation, 

Certain  relations  are  likewise  observable  on  comparing  the  heats  of 
combustion  of  different  substances,  molecule  for  molecule.  Thus  the 
molecular  heat  of  combustion  increases  in  most  homologous  series  by 
150,000  to  160,000  calorimetric  units  for  each  atom  of  carbon. 

In  isomeric  compounds  the  heats  of  combustion  are  equal  when  the 
chemical  nature  of  the  compounds  is  the  same,  e.g.  in  the  case  of 
methyl  acetate  and  ethyl  formate,  but  different  when  the  constitution  is 
different ;  thus  the  heat  of  combustion  of  acetone  is  greater  than  that  of 
allyl  alcohol,  and  that  of  di-propargyl  materially  higher  than  that  of 
benzene. 

From  the  heat  of  combustion  the  heat  of  formation  of  a 
substance,  which  is  very  closely  connected  with  its  constitution^ 
can  be  calculated.  For  particulars  of  these  interesting  rela- 
tions, Thomsen's  "  Thermochemische  Untersuchungen,"  vol.  4, 
must  be  consulted. 

O^ptical  Behaviour, 

1.  Refractive  power.  As  Molecular  refractive  power  or  refraction  equi- 
valent is  designated  the  product  of  the  molecular  weight  M  into  the 

specific  refractive  power  of  a  liquid,  — — ,  that  is  M  .       ^  (/^  being  the 

P  P 
index  of  refraction  and  p  the  density  of  the  liquid). 

For  the  molecular  refractive  power,  which  is  independent  of  the 
temperature,  similar  laws  hold  good  as  for  the  molecular  volume.  (1) 
In  homologous  series  it  increases  continuously  by  about  7 '6  for  every 
CHg.  (2)  It  is  almost  the  same  for  isomeric  compounds.  (3)  The 
molecular  refractive  power  of  compounds  is  approximately  equal  to  the 
sum  of  the  refractive  equivalents  of  the  elements  which  are  deduced 
from  it,  as  the  atomic  volumes  are  from  the  molecular  volumes. 

This  relation  is,  as  stated,  only  an  approximate  one,  the  mode  in 
which  the  atoms  are  combined  appearing  to  influence  it.  Brilhl  states 
that  the  molecular  refractive  powder  of  unsaturated  compounds  is  greater, 
with  approximate  regularity,  than  the  value  calculated  as  above  (A. 
200, 139;  203,  263);  thus  the  determination  of  the  refraction  equivalent 
becomes  a  means  of  elucidating  the  constitution  of  organic  compounds. 

2.  Behaviour  towards  Polarized  Light  {Circular 
Polarization). 

Many  organic  compounds  turn  the  plane  of  polarization  of 
light.  Some  only  effect  this  when  in  the  solid  state  and  not 
when  fused  or  dissolved,  thus  showing  that  the  property 


OPTICAL  BEHAVIOUR. 


31 


depends  upon  their  crystalline  structure,  e.g,  benzil^  0^411^^02 ; 
others  both  when  solid  and  in  solution,  e.g.  sulphate  of  strych- 
nine ;  most  of  them,  however,  only  when  liquid,  e.g.  tartaric 
acid,  cane  sugar,  etc.  Oil  of  turpentine  and  camphor  also 
possess  this  property  when  in  the  state  of  gas,  and  it  must 
therefore  in  their  case  be  dependent  upon  the  arrangement  of 
the  atoms  and  not  of  the  molecules. 

It  has  now  been  proved  in  many  cases  that  several  optically 
different  modifications  of  the  same  compound  exist ;  there  are, 
for  instance,  a  dextro-rotatory  and  an  equally  strong  laevo- 
rotatory  tartaric  acid,  by  the  combination  of  which  an  inactive 
tartaric  acid  (racemic  acid)  is  formed.  The  last-named  can  be 
broken  up  into  the  two  active  modifications,  in  contradistinction 
to  another  inactive  tartaric  acid  which  is  not  thus  divisible. 
When  the  active  compounds  which  occur  in  nature  are  pre- 
pared artificially  in  the  laboratory  they  are  almost  always 
inactive,  but  these  inactive  modifications  can  frequently  be 
either  transformed  or  split  up  into  the  active,  e.g.  inactive  into 
ordinary  tartaric  acid  by  heating  with  water  to  170°.  Such 
transformation  or  splitting  up  can  sometimes  be  effected  by 
the  crystallization  of  salts  of  the  acids,  e.g.  the  cinchonine 
salts  and  the  double  Na-NH^-racemate,  and  also  by  the  addition 
of  certain  ferments,  in  especial  the  Penicillium  glaucum  and  the 
Schizomycetes.  The  action  of  the  latter  is  explained  by  their 
destroying  the  one  active  modification  more  rapidly  than  the 
other.  For  the  characteristic  faces  on  such  salts,  see  tartaric  acid. 

Such  optically  different  modifications  may  also  show  slight 

differences  in  their  chemical  relations.     According  to  Le  Bel 

and  van  H  Hoff,  the  optical  activity  is  determined  by  the 

presence  of  one  or  more  asymmetric  carbon  atoms,  i.e.  carbon 

atoms  which  are  joined  by  their  four  affinities  to  four  different 

elements  or  groups,  as,  for  instance,  in  active  amyl  alcohol  (I.), 

and  in  tartaric  acid  (II.)  : 

CH3  HO  OH 

I  II 
(L)H— C-CgH^;        (II.)  HC  — CH  . 

i  I  I 

0  CO2H  CO2H 


32 


INTRODUCTION. 


As  a  matter  of  fact  all  optically  active  substances  contain  such 
asymmetric  carbon  atoms,  but  not  vice  versa. 

For  the  explanation  of  optical  activity  upon  this  ground, 
see  van  HHoff's  Lagerung  der  Atome  im  Raume,"  Braun- 
schweig, 1877. 

The  turning  of  the  plane  of  polarization  is  proportional 
(1)  to  the  thickness  of  the  layer  of  the  solution  to  be  traversed, 
and  (2)  to  the  percentage  of  compound  in  it.  If  the  observed 
angle  of  deflection  a  be  reduced  to  the  length  of  1  decimetre 
of  the  layer  traversed,  and  to  1  gramme  of  the  active  substance 
in  1  cubic  centimeter  of  solution  (a  =^p/100,  where  p  =  the  speci- 
fic gravity  of  the  solution),  then  the  "  specific  rotatory  power  " 

of  the  substance  is  :        r  -,  100a 

[a]  =  . 

l.;p.p. 

This  specific  rotatory  power  to  right  (  +  ),  or  to  left  (  -  ),  is 
constant  and  characteristic  for  each  substance  dissolved  in  a 
given  solvent,  and  of  a  given  concentration  and  temperature. 
It  diminishes  as  a  rule  with  rise  of  temperature,  and  increases 
with  increasing  dilution,  and  it  is  also  dependent  upon  the 
nature  of  the  solvent  and  of  any  possible  admixture. 

Thus  asparagine  and  aspartic  acid  in  alkaline  solution  turn  the  plane 
to  the  left,  in  acid  solution  to  the  right.  Dextro-tartaric  acid,  with  in- 
creasing concentration  of  the  solution,  turns  it  less  and  less  to  the  right; 
when  it  contains  100  per  cent.,  i.e.  when  fused,  it  turns  it  to  the  left. 

By  eliminating  the  (calculated)  influence  of  the  solvent,  we 
obtain  the  "real  specific  rotation"  (LandoU).  This  is  usually 
given  for  yellow  sodium  light,  i.e.  Fraunhofer^s  D-line,  and 
designated  as  [aj^. 

These  optical  relations  are  sometimes  complicated  by  the  pre- 
sence of  the  so-called  "Bi-rotation."  (See  grape  and  milk  sugars.) 
(Cf.  Landolt,  "Das  optische  Drehungsvermogen  organischer  Sub- 
stanzen,"  Braunschweig,  1879.) 


SPECIAL  PART. 


(50U) 


Class  I -METHANE  DERIVATIVES. 


I.  HYDROCARBONS. 


A.  Saturated  Hydrocarbons,  C^^Hgn+s. 

Summary. 


CH4 
C2H6 


C4H10 
C4H10 

^7^1(5 

C10H22 
C11H24 


Methane, 

Ethane. 

Propane, 

Butanes. 

(1)  Normal- 
butane, 

(2)  Iso- 
butane, 

Pentanes. 

(1)  Normal- 
p'^ntane, 

(2)  Iso- 
pentane, 

(3)  Tertiary- 
pentane, 

Hexane, 

Heptane, 

Octane, 

Nonane, 

Decane, 

Undecane, 

Doclecane, 


M.Pt.  B.Pt 


186^ 


-20° 


-51° 
-32° 
-26° 
-12° 


-164^ 

Gas. 

-17° 


+  1° 
-17° 

+  37° 
-f30° 

+  9° 

69°-^ 
98° 
124° 
150° 
173° 
195° 
214° 


13^28 

^6^34 
^171136 

C19H40 
C20H42 
C21H44 

^23^48 
^24^50 

C32H66 
^35-'^^72 


Tri  decane, 

Tetradecane, 

Pentadecane, 

Hexadecane, 

Heptadecane, 

Octadecane, 

Nonadecane, 

Eicosane, 

Heneicosane, 

Docosane, 

Tricosane, 

Tetracosane, 

Heptacosane, 

Hentriacon- 

tane, 
Dicetyl, 

Penta-tria- 
contane, 


M.Pt.  B.Pt. 


-6° 
+  5° 
-f  10° 
18° 
23° 
28° 
32° 

37° 
40° 
44° 
48° 
51° 

60° 

68° 

70° 


75° 


234° 
253° 
271° 
288° 
303° 
317° 
330° 
{205°t 
1215° 
{225° 
{234° 
{243° 

{270" 

{302° 

{310° 


331° 


*  All  the  numbers  given  from  hexane  onwards  refer  to  the  normal 
hydrocarbons.    (See  below. ) 

t  I  signifies  boiling  point  under  15  mm.  pressure. 


SATURATED  HYDROCARBONS. 


35 


Tlie  first  members  of  the  series  up  to  those  with  about  four 
atoms  of  carbon  are  gases,  which  gradually  become  more  easily 
condensable  as  the  number  of  carbon  atoms  in  the  molecule 
increases.  The  members  which  follow  are  liquid  at  the  ordi- 
nary temperature,  their  boiling  point  rising  with  increasing 
number  of  carbon  atoms.  The  higher  homologues,  from  about 
Cj,;H34  (melting  point  18°)  on,  are  solid  at  the  ordinary  tem- 
perature. The}^  boil  finally  without  decomposition  only  under 
diminished  pressure  and  at  very  high  temperatures,  while  their 
melting  point  gradually  rises  till  it  reaches  75°.  The  methane 
homologues  are  almost  or  quite  insoluble  in  water ;  alcohol 
dissolves  the  gaseous  members  to  a  slight  extent,  the  liquid 
members  easily,  and  the  solid  with  gradually  increasing 
difficulty.  Their  specific  gravities  at  the  melting  point 
increase  with  increasing  number  of  carbon  atoms  from  0*4 
up  to  0*78,  which  forms  a  boundary  limit.  This  value  is 
already  almost  reached  by  the  hydrocarbon  C^^H24,  so  that 
for  the  higher  members  of  the  series  the  following  law  holds 
good  :  '^the  molecular  volumes  are  proportional  to  the  specific 
gravities,"  (Kmfft). 

They  are  incapable  of  combining  further  with  hydrogen  or 
halogens  (see  p.  21),  and  absorb  neither  bromine  nor  sulphuric 
acid.  They  are  therefore  termed  the  Saturated  Hydro- 
carbons. Even  fuming  nitric  acid  has  little  or  no  action 
upon  them  ;  thus,  methane  is  not  attacked  by  a  mixture  of 
fuming  nitric  and  sulphuric  acids,  even  at  150°.  They  are 
also  very  indifferent  towards  chromic  acid  and  permanganate 
of  potash  in  the  cold ;  when  oxidation  does  take  place,  they 
are  mostly  converted  directly  into  carbonic  acid.    The  name  of 

The  Paraffins,"  (from  parum  affinis),  which  was  originally 
applied  only  to  the  solid  hydrocarbons  from  lignite,  has  there- 
fore been  extended  to  the  whole  homologous  series. 

By  the  action  of  the  halogens,  (CI,  Br),  substitution  takes 
place,  the  substituted  hj^drogen  combining  with  an  amount  of 
halogen  equal  to  that  which  has  entered  the  hydrocarbon, 
(see  Substitution  products  of  the  Hydrocarbons)  : 

CH3H  -h  GlOl  =  CH3CI  -h  HCl. 


36 


I.  HYDROCARBONS. 


The  percentage  composition  of  these  hydrocarbons  ap- 
proaches with  increasing  carbon  to  a  definite  limit,  viz.  to 
that  of  the  hydrocarbons,  Cj^Hgu,  =  CHg,  as  is  shown  by  the 
following  table  : 


Per 
cent. 

CH4 

^2^6 

C3H8 

^^61114 

^22^46 

^^241150 

^35^72 

Limit 
Value, 

C 
H 

75-00 
25  00 

80  00 
20-00 

81-82 
18-18 

83-72 
16-28 

84-60 
15-40 

85-16 
14-84 

85-21 
14-79 

85-36 
14-64 

85-71 
14-29 

It  is  therefore  impossible  to  distinguish  by  elementary 
analysis  between  two  of  the  neighbouring  higher  homologues, 
e.g.  and  C24,  C24  and  G^q  ;  the  only  reliable  data  here  are 
the  methods  of  formation  from  compounds  in  which  the 
number  of  carbon  atoms  in  the  molecule  is  already  known, 
and  the  melting  points. 

homers. — Only  one  representative  each  of  the  formulae 
CH^,  C2H(.,  and  CgHg  is  known,  but  of  C^H^q  there  are  two, 
of  C5HJ2  three,  and  of  C^^^H^^  already  five  isomers,  and  most  of 
the  higher  hydrocarbons  are  known  in  various  isomeric  forms. 
From  this  the  conclusion  is  drawn  that  in  these  difi'erent 
isomers  the  carbon  atoms  are  difi'erently  combined,  in  the  one 
case,  as  it  were,  in  a  straight  line  without  branching,  like  the 
links  of  a  chain  ;  in  the  other,  with  the  formation  of  a  branch- 
ing chain.  (This  is  of  course  not  to  be  taken  as  meaning 
that  they  are  grouped  together  in  space  in  straight  lines.) 
Thus  : 

C—C— 0— C-C,  or  g>C  <^  or  C— C— C<^ 

The  first  of  these  hydrocarbons,  with  a  non-branching  chain, 
are  termed  the  normal  hydrocarbons  ;  the  last,  the  iso-hydro- 
carbons.    (See  p.  41.) 

The  principles  by  which  such  constitutional  formulae  are 
arrived  at  will  be  explained  under  Butane  and  Pentane. 

Only  those  homologues  are  comparable  whose  constitutions  are 
similar,  as  in  the  case  of  the  normal  hydrocarbons. 

Occurrence. — The  hydrocarbons  of  the  paraffin  series  occur 
naturally  in  great  variety.    Thus,  methane  is  exhaled  from 


0(UinRl{KN(!K  ;  MODKS  OK  FOPvMATION. 


37 


the  earth's  crust,  .is  i)it  gas  and  as  marsh  gas.  The  next 
higher  liomologucs  are  found  dissolved  in  petroleum,  which 
also  contains  the  higher  hydrocarbons  in  large  amount.  Solid 
hydrocarbons  occur  as  ozokerite  or  earth  wax.  By  the  frac- 
tional distillation  of  petroleum,  a  large  number  of  these  com- 
pounds have  been  isolated.  Heptane  and  hexadecane  are  also 
found  in  the  vegetal)le  kingdom. 

Modes  of  formation. — A.  The  gaseous  as  well  as  the  liquid 
and  solid  members  of  this  series  are  obtained  by  the  distilkition 
of  lignite  (Boghead-,  Cannel  coal),  wood,  bituminous  shale, 
and,  in  very  much  smaller  quantity,  from  pit  coal.  Paraffins 
are  also  got  by  dissolving  carbide  of  iron  in  acids,  and  by 
heating  wood,  lignite,  and  coal,  but  not  graphite,  with 
hydriodic  acid. 

B.  From  substances  containing  an  equal  number  of  carbon 
atoms  in  the  molecule. 

1.  From  the  halogen  alkyls,"^  C^Hga+iX,  and,  generally 
speaking,  from  the  substitution  products  of  the  hydrocarbons 
by  exchange  of  the  halogen  for  hydrogen,  (backward  substitu- 
tion). This  is  effected  by  the  action  of  sodium  amalgam,  or 
of  zinc  and  hydrochloric  acid,  by  heating  with  water  and  zinc 
to  160°,  (Frankland),  or  with  fuming  hydriodic  acid,  which  last 
is  a  most  energetic  reducing  agent,  especially  in  the  presence 
of  red  phosphorus  ;  and  so  on. 

Heating  with  anhydrous  chloride  of  aluminium  has  a  similar  effect.  ^ 

02H6l  +  HH  =  C2Hfi  +  HI. 

CH3I  +  HOH  +  Zn  =  CH4  +  Zn  | 

C2H5I  +  HI  =  C^H,  + 1^.   ^  -r^^  .  . 

^    ^  ^    o      z     Basic  iodide  of  zinc. 

2.  From  the  monatomic  alcohols,  C^Hgn+iOH. 

a.  By  first  converting  them  into  the  corresponding  halogen 
compounds,  e.g,  by  means  of  halogen  hydride,  and  then  trans- 
forming those,  according  to  1,  into  the  paraffins. 

Kmfft  has  prepared  the  higher  normal  paraffins  from  these 

*The  monovalent  residues,  CnH2ii4-i,  methyl,  ethyl,  etc.,  which  are  at 
the  same  time  the  radicles  of  the  monatomic  alcohols,  CnH2n+iOH,  are 
frequently  termed  alkyls. 


38 


I.  HYDROCARBONS. 


lialogen-alkyl  compounds,  by  splitting  off  the  halogen  hydride 
and  heating  the  residual  C,,Ho,,  with  HI.    (B.  16,  1714.) 
h.  By  heating  directly  with  hydriodic  acid — 
C^H.OH  +  2HI  -  C^H.I  +  H^O  +  HI  =  C^H,  +  H^O  +  1^, 

3.  Also  by  heating  polyatomic  alcohols,  such  as  glycerine, 
with  hydriodic  acid  to  a  high  temperature. 

4.  From  compounds  richer  in  oxygen,  such  as  aldehydes,  ketones 
and  acids,  by  heating  them  to  a  high  temperature,  e.g.  280°,  with 
hydriodic  acid  saturated  at  0°  and  amorphous  phosphorus.  The  above 
compounds  are  frequently  converted  in  the  first  instance  into  the  cor- 
responding chlorides  by  means  of  phosphorus  pentachloride.  ' 

5.  From  hydrocarbons  poorer  in  hj^drogen,  i.e.  unsaturated 
hydrocarbons  (see  these),  by  the  addition  of  nascent  hydrogen  ; 
e.g.  ethane  from  ethylene  or  acetylene  and  hydrogen,  either 
in  presence  of  platinum  black  or  by  heating  the  mixture  of 
gases  to  400''-500°.  Also  by  heating  with  hydriodic  acid, 
(see  above,  3),  or  by  addition  of  halogen  or  halogen  hydride, 
and  exchange  of  the  halogen  for  hydrogen,  according  to  1. 

^^^^^  '  CgH^  +  H9  =  ^2^6^ 

(  C^H,  +  HBr  =  CgHgBr, 
tc,H,Br  +  H2  =  C,H,  +  HBr. 

C.  From  acids  containing  more  carbon,  with  separation  of 
carbon  dioxide.    Thus,  by  heating  acetate  of  calcium  with  , 
soda-lime,  methane  and  carbonic  acid  are  formed  : 

CHgCOONa  +  NaOH  =  CH^  +  Na^COg. 

D.  By  the  combination  of  two  radicles  containing  a  smaller 
number  of  carbon  atoms. 

1.  By  the  action  of  sodium  upon  the  alkyl  iodide  in  ethereal 
solution,  {FTurtz),  see  p.  16  ;  or  by  heating  with  zinc  in  a  sealed 
tube,  (FranJdtmd)  : 

pXT  T  CJHg 

PH^  +  Na2=  r  +2NaI. 

By  this  method  also  two  different  radicles  can  be  combined, 
e.g.  CoH.I  +  C^HjjI  give  C^H^  +  CJi^  =  C^Hi^,  ethyl-butyl, 
(JFurtz'    Mixed  Radicles''). 


MCTIfANl^]. 


39 


2.  By  the  action  of  halogen  alkyl  upon  zinc  alkyl,  whereby  dissimilar 
radicles  may  also  be  united — 


2^-"  =  Znl2  +  2CH3.CH3. 


3.  By  the  electrolysis  of  acids  of  the  acetic  acid  series, 
(Kolbe,  1848) : 

CH3-COOH     __^^3  -p. 
CH3-COOH    -^jj  +^^^2+^2- 

The  hydrogen  is  here  evolved  at  the  negative  pole,  and  the 
hydrocarbon  and  carbon  dioxide  at  the  positive. 


Methane,  (Fl^te,  1778).  Occurrence.  As  an  exhalation 
from  the  earth's  crust,  more  especially  at  Baku  in  the  neigh- 
bourhood of  the  Caspian  Sea  (the  Holy  Fire  "  of  Baku) ;  on 
the  peninsula  of  Apscheron,  where  it  is  used  for  heating  pur- 
poses in  the  Tartar  village  of  Balachana ;  in  North  America, 
e.g.  from  the  large  gas  wells  at  Pittsburg,  such  as  the  Burns 
well  (see  Ethane) ;  in  Italy  ;  near  Glasgow ;  in  the  exhalations 
from  mud  volcanoes,  for  instance,  at  Bulganak  in  the  Crimea, 
where  the  gas  is  almost  pure  methane,  (JBunsen),  and  so  on. 

As  pit  gas  in  mines,  where  it  causes  explosions. 

As  marsh  gas,  produced  along  with  CO^  and  N  by  the 
decomposition  of  organic  substances  under  water ;  further,  by 
the  fermentation  of  cellulose,  e.g.  by  river  mud  (by  means  of 

Bacillus  amylobacter  "). 

It  is  also  found  in  rock  salt  (the  Knistersalz  of  Wieliczka), 
and  in  the  human  intestinal  gases,  (up  to  57  per  cent.  CH^ 
after  eating  pulse). 

The  illuminating  gas  obtained  by  the  destructive  distillation 
of  coal  contains  about  40  per  cent,  methane. 

Modes  of  preparation.  1.  Methane  is  formed  synthetically 
in  an  indirect  manner  by  the  union  of  carbon  and  hydrogen 
to  acetylene  at  the  temperature  of  the  electric  arc,  the 
subsequent  transformation  of  this  into  ethane,  and  of  the  latter 
into  methane  at  a  red  heat,  {Berthelot),  thus  : 

C2H2  +  2H2  =  C2He ;  C2Hg  =  CH^  +  C  +  Hg. 

2.  From  carbon  monoxide  and  hydrogen  under  the  influence  of 
electricity  ;  CO  +  3FI,^  -  CH^  4-  Kp. 


40 


1.  HYDROCARBONS. 


3.  By  leading  sulphuretted  hydrogen  and  carbon  bisulphide  over  red- 
hot  copper  ;  CS^  +  2H2S  +  8Cu  =  CH4  +  4Cih,S. 

4.  Preparation  from  acetic  acid,  (Bunsen).  Sodium  acetate 
is  heated  with  baryta  or,  less  advantageously,  with  soda-lime 
,(cf.  p.  38),  ethylene,  CgH^,  and  hydrogen  (up  to  8  per  cent.), 

being  formed  at  the  same  time.  Acetic  acid  may  also  be  made 
to  yield  methane  by  a  process  of  fermentation. 

5.  Methane  is  obtained  chemically  pure  from  zinc  methyl 
and  water ;  also  (see  B,  1)  by  the  reduction  of  methyl  iodide, 
CH3I,  e.g.  in  alcoholic  solution  by  means  of  zinc  in  the 
presence  of  precipitated  copper,  (the  Gladstone-Tribe  Copper- 
zinc  Couple  ") ;  ^  also  by  the  backward  substitution  of  chloro- 
form, CHCI3,  or  carbon  tetrachloride,  CCL. 

1 6 

Properties.  Gas,  Sp.  Gr.  0*559  (  =  §8^'  ^'  ^^^^ 
condensable  under  a  pressure  of  140  atmospheres  at  0°.  Boils 
at  -164°,  and  solidifies  at  -186°.  Absorption  coefficient  in 
cold  water  about  0*05,  in  cold  alcohol  0*5.  Burns  with  a  pale 
and  only  faintly  luminous  flame.  Is  decomposed  by  the 
electric  spark  into  carbon  and  hydrogen.  Splits  up  for  the 
most  part  into  its  elements  on  being  led  through  a  red  hot 
tube,  but  there  are  formed  at  the  same  time  CgH^^,  CgH^,  ^2^2^ 
and,  in  smaller  quantity,  CgHg,  benzene,  C^oHg,  naphthalene, 
and  other  products.  The  first  three  hydrocarbons  just  men- 
tioned, ethane,  etc.,  behave  similarly. 

Ethane,  G^^cy  Occurrence.  In  crude  petroleum.  Con- 
stitutes, for  example,  the  gas  of  the  Delamater  gas  well  in  Pitts- 
burg, and  is  there  utilized  for  technical  purposes. 

Preparation.  By  the  electrolysis  of  acetic  acid,  {Kolhe,  1848), 
and  therefore  formerly  called  methyl "  ;  also  from  ethyl 
iodide,  alcohol,  and  zinc  dust,  or  from  zinc  ethyl,  (Frankland), 
hence  the  name     ethyl  hydride."    "  Ethyl  hydride "  and 

methyl,"  which  were  formerly  supposed  by  Frankland  and 
Kolhe  to  be  different  substances,  were  proved  to  be  identical  by 
Schorlemmer  in  1863  by  their  conversion  into  C2H5CI. 

^  This  is  a  special  preparation  of  zinc  coated  with  copper  precipitated 
from  a  solution  of  copper  sulphate,  which  acts  much  more  energetically 
than  zinc  alone.    (Ch.  Soc.  J.  1884,  154.) 


KTTTANK,  ETC.  ;  TSOMERTSM. 


41 


Properties.  Gas,  c()n(lcnsal)lc  under  a  prcssuro  of  40  atmos- 
pheres at  4°;  soiTiovvhat  more  soluble  than  nietliane  in  water 
and  alcohol.    Burns  with  a  faintly  luminous  flame. 

Propane,  CgHg.  Present  in  crude  petroleum,  and  liquid 
below  -  17°.  Preparation.  By  the  action  of  hydriodic  acid  on 
acetone  or  glycerine  (Berthelot),  thus  : 

C3H^  +  2H,  =  C3H8  +  H20; 

Acetone. 

C3H303  +  3H2  =  C3H3  +  3H20; 

Glycerme. 

or  from  isopropyl  iodide  with  zinc  and  hydrochloric  acid. 

Butane,  C^H^q.  Two  isomeric  butanes  exist.  Normal 
butane  boils  at  +1°,  and  has  the  Sp.  Gr.  0*60  at  0° ;  isobutane 
boils  at  -  17°. 

Normal  butane,  which  is  also  present  in  petroleum,  can  be 
prepared  by  the  action  of  sodium  amalgam  or  zinc  upon  ethyl 
iodide,  C2H5I,  (Frankland),  and  has  therefore  the  following 
constitution  : 

CH3— CH2— CH2— CH3  (di-ethyl)  : 
CH3— OH2I  ,  _  CH3— CH2  2NaT 

+  CH3— CH2I  +  ^^^2  -  CH3— CH2  ^ 

Isobutane  is  formed  from  isobutyl  iodide,  C^Hgl,  {Wurtz), 
according  to  B,  1,  and  also  by  the  action  of  zinc  and  water 
upon  tertiary  butyl  iodide,  (which  see),  (Butlerow). 


Isomerism,  Nomenclature,  Constitution. 

The  Isomerism  of  the  two  butanes  is  explained  on  the 
assumption  that  in  isobutane  the  carbon  atoms  are  not  com- 
bined witli  one  another  in  a  "  continuous  straight  line  "  but  in 
a    branching  "  one,  according  to  the  formula : 
CH3 
I 

CH— CH3,  =  CII(CH3)3, 
CH3 


42 


I.  IIYDTiOCARBUNS. 


which  corresponds  with  the  name  tri-ra ethyl-methane.  (See 
below.)  The  evidence  for  this  rests  upon  the  proof  of  the 
constitution  of  tertiary  butyl  iodide,  C^B^)!.    (Cf.  p.  43.) 

These  two  butanes  are  theoretically  the  only  possible  ones 
of  the  formulae  C^H-^q. 

All  the  succeeding  hydrocarbons  can,  according  to  theory, 
exist  in  various  isomeric  modifications.  Thus  theoretically 
three  pentanes  should  exist,  and  as  a  matter  of  fact  three  are 
known.  Of  hydrocarbons  with  six  carbon  atoms,  five  isomers 
are  possible,  and  they  are  all  known.  Of  the  nine  possible 
heptanes,  CyH^^.,  the  existence  of  five  has  already  been  proved. 

The  number  of  theoretically  possible  isomers  increases  very 
rapidly  with  increasing  carbon,  so  that,  according  to  Cayley, 
802  isomeric  hydrocarbons  of  the  formula  G^^^^  are  possible. 

Of  these  isomers  only  one  can  be  normal,  i.e.  can  have  a 
carbon  chain  in  a  continuous  straight  line  (p.  36),  in  which 
each  of  the  two  carbon  atoms  at  either  end  are  combined  with 
three  atoms  of  hydrogen,  and  all  the  middle  ones  with  two, 
according  to  the  formula  : 

CH3 — (CHa)^ — CH3. 

A  convenient  Nomeiiclature  for  the  more  complicated 
paraffins  is  arrived  at  by  making  methane  the  starting  point 
for  all  of  them,  that  carbon  atom  from  which  the  branching 
chain  emanates  being  considered  as  originally  belonging  to 
in  which  the  hydrogen  atoms  are  supposed  to  be  wholly 
or  partially  replaced  by  hydrocarbon  radicles,  thus  : 

/CHo 

CH^CH3  =  Dimethyl-ethyl-methane. 

The  names  of  the  well  known  lower  hydrocarbon  radicles 
(alkyls)  are  also  frequently  used  as  a  basis ;  for  instance,  the 
group  (CH3)2CH  is  termed  isopropyl,  (see  Iso-propyl  Alcohol), 
hence  the  compounds  : 

^j[j3\>CH— CH2— CH3 :  Ethyl-isopropyl. 
^ JJ^>CH— CH<^ .  Di-isopropyl. 


NOMIONCLATIJKK  ;  ( ;( JNSTITU'J'K  )N. 


43 


Schorlemmer  diistiu'^'uishes  between  tlie  following  four  ekisses  of 
paraffins  : — 

1.  Normal  paraffins. 

2.  Iso-paraffins,  in  which  one  assumes  a  single  branching  in  the 
molecule. 

3.  Meso-paraffins,  with  several  of  such  branchings. 

4.  Neo-paraffins,  containing  one  carbon  atom  to  which  four  others  are 
united. 

The  boiling  points  of  the  normal  hydrocarbons  are  always 
higher  than  those  of  the  isomers ;  indeed  the  boiling  point 
becomes  lowered  continuously  the  more  the  carbon  atom  chain 
is  branched,  i.e.  the  more  methyl  groups  arc  gathered  together 
in  the  molecule. 

The  Constitution  of  the  higher  paraffins  can  in  most  cases  only 
be  arrived  at  with  certainty  from  their  synthetical  formation, 
(e.g.,  normal  butane  and  hexane),  or  from  their  chemical 
relation  to  oxygenated  derivatives  whose  constitution  is  already 
known,  especially  to  the  ketones  and  acids.    (See  Ketones.) 

If,  for  instance,  by  the  action  of  PCl^  upon  acetone,  for 
which  the  constitution  CH3 — CO — CH3  is  proved,  the  sub- 
stance (CH3)2CCl2,  =  CH3 — CClo — CH3  (acetone  chloride)  be 
formed,  and  this  be  then  treated  with  zinc  methyl,  the  resulting 
hydrocarbon,  a  pentane,  will  have  the  constitution  (0113)^0  : 

gi;>c<g!-g|>ZB  =  ^i;>c<^i;+znci. 

The  same  hydrocarbon,  tetra-methyl-m ethane,  is  also  pro- 
duced by  the  action  of  zinc  methyl  on  tertiary  butyl  iodide, 
(see  this  and  also  p.  42),  from  which  it  follows  that  the  con- 
stitution of  the  last-named  compound  is  (0113)301 : 

OHgx  *  OHgx 

CHg-^OI  -1-  znOHo  =  0H3-^0— OH,  +  znl. 

OH3/  OH3/ 

And,  since  tertiary  butyl  iodide  is  converted  by  nascent 
hydrogen  into  isobutane,  the  formula  of  the  latter  is  thus 
proved  to  be  (OH3)30H. 

The  same  constitution-formula  for  tertiary  butyl  iodide  is  arrived  at 
from  that  of  tertiary  butyl  alcohol.    (See  these.) 


44 


I.  HYDROCARBONS. 


Pentanes.  According  to  theory,  and  also  in  reality,  three 
isomeric  pentanes  exist.    (See  table.) 

1.  Normal  pentane,  CH3 — CR^—CU^ — CHg— CH3. 

2.  Isopentane,  ethyl-isopropyl,''  (CH3)2=CH — CHg — CH3, 
(from  iso-amyl  iodide.) 

3.  Tetra-methyl-methaney  G(GIi^)^. 

The  two  first  are  contained  in  petroleum.  (That  portion  of 
the  petroleum  distillate  which  boils  under  0°  is  used  as  an 
anaesthetic  under  the  names  rhigolene  and  cymogene,  and 
also  in  the  preparation  of  ice.)  Isopentane  is  formed  from 
amyl-iodide,  according  to  B,  1.  For  tetra-methyl-methane,  see 
above. 

Hexanes,  CgH^^.  The  five  hexanes  known  boil  between 
46°  and  71°.  Normal  hexane  is  produced,  among  other 
methods,  by  the  action  of  hydriodic  acid  upon  mannite, 
CqR^JJq,  and  also  upon  aniline,  CgH^N.  Its  constitution 
follows  from  its  formation  from  normal  propyl  iodide, 
CH3.CH2.CH2I,  and  sodium,  in  a  manner  analogous  to  that 
of  normal  butane. 

Normal  heptane,  C^H^g,  B.Pt.  98°,  is  present,  for  instance, 
in  the  ethereal  oil  of  Pinus  Sabinia,  the  Californian  nut  pine. 
It  has  a  strong  smell  of  oranges  and  produces  insensibility 
when  breathed. 

From  petroleum  have  been  separated  the  two  first- mentioned 
pentanes,  also  normal  hexane  and  an  isomer,  both  being  pre- 
sent in  the  so-called  "  gasoline,"  which  is  obtained  by  the 
distillation  of  petroleum,  and  is  used  for  carbonizing  coal  gas ; 
further,  normal  Heptane,  n-Octane,^  n-Nonane,  and  n-Decane, 
besides  an  isomer  of  each,  and  in  addition  to  these  (as  also 
from  the  distillation  of  cannel  and  Boghead  coal),  a  large  number 
nominally  of  the  higher  hydrocarbons,  (CahourSy  Pelouze^ 
Warren,  Schorlemmer). 

In  all  probability  these  products  are  not  chemical  individuals 
but  an  inextricable  mixture  of  homologues  and  isomers  stand- 

*  The  petroleum  ether  and  ligroin  of  commerce  consist  principally  of 
the  hydrocarbons  C(jHi4,  CyH^g,  and  CgHig. 


TIIK  IlKJIIiai  JIYDllOCAUliUNS. 


45 


iiig  very  near  to  each  other,  as  is  sliowii  by  a  comparison  with 
the  artificially  prepared  normal  hydrocarbons.    (See  below.) 

F.  Kraft  has  prepared  the  whole  series  of  normal  hydro- 
carbons (see  table),  from  to  C25Hr,2i  and  also  those  with 
27,  31,  and  35  atoms  of  carbon,  from  the  acids  C^g'  ^14?  ^10 
and  C^g  of  the  acetic  acid  series,  (see  these),  for  which  the 
normal  constitution,  i.e.  non-branching  carbon  chain,  has  been 
demonstrated  ;  and  also  from  the  ketones,  CnHgnO,  which  are 
obtained  by  subjecting  the  barium  salts  of  these  acids  to  dry 
distillation,  either  alone  or  together  with  acetate  or  lieptoate 
of  calcium,  and  which,  as  a  consequence  of  their  mode  of  for- 
mation, yield  normal  hydrocarbons.  (See  Ketones.)  These 
are,  from  about  G^Ji^^^  (M.  Pt.  18°)  on,  solid  at  the  ordinary 
temperature.  Upon  distillation  under  the  atmospheric  pressure, 
the  higher  hydrocarbons  partially  decompose  into  lower  ones  of 
the  formulae  GJi2n+2  and  CnHgn^,  but  they  may  be  distilled  in 
a  vacuum,  whereby  their  boiling  points  are  reduced  by  100°  or 
more.    (See  table.) 

Petroleum,  Earth  Oil — This  is  produced  by  the  decomposition  of 
animal  organisms  {EngUr).  It  is  found  between  Pittsburg  and  Lake 
Erie  in  America  ;  between  Lake  Erie  and  Lake  Huron  in  Canada  ; 
in  Hanover,  Holstein,  and  Elsass  in  Germany  ;  in  Boryslaw  by  Dro- 
hobycz  in  GaHcia ;  in  the  Crimea  ;  in  the  Caucasus,  where  the  oil 
fountains  rise  to  a  height  of  9  metres  in  summer  ;  etc. 

The  specific  gravity  of  the  Pennsylvanian  oil,  after  purification  by 
treatment  with  caustic  soda  and  sulphuric  acid  and  subsequent  distilla- 
tion, is  0-79  to  0-81,  and  its  boihng  point  200°-300°.  The  Canadian  oil 
has  a  higher  specific  gravity,  and  contains  substances  of  a  very  un- 
j)leasant  odour.    Petroleum  has  been  a  commercial  product  since  1848. 

It  must  not  be  forgotten  that  all  earth  oils  do  not  possess  a 
similar  composition.  While  the  American  oil  consists  almost 
entirely  of  paraffins,  recent  investigations  have  shown  that 
petroleums  from  other  sources,  especially  those  from  the 
Caucasus  and  Galacia,  contain  for  the  most  part  other  hydro- 
carbons, a  mixture  of  "  naphthenes  "  {GJl^n^  see  olefines  and 
hexa-hy  dro-benzene) . 

Paraffin,  obtained  by  Beichenhach  in  1830  from  wood  tar,  is  got  by 

*  The  hydrocarbons  undergo  a  similar  decomposition  upon  treatment 
with  AlgBrg  +  HI  ;  e.g.  CqRu  yields  C4H8  and  OaHgBr. 


46 


I.  HYDROCARBONS. 


the  distillation  of  lignite  or  peat.  It  also  is  a  mixture  of  many  hydro- 
carbons, about  40  per  cent,  of  it  consisting  of  the  compounds  C22H4g, 
^24^50 5  CogHgo,  and  C28H58. 

Liquid  Paraffin  {ReichenhacK' s  Eupion  ")  and  the  butter-like  Vase- 
line are  high-boiling  distillation  products  of  lignite  or  petroleum,  and 
the  same  applies  to  many  lubricating  oils. 

Ozokerite,  green,  brown,  and  red,  and  of  the  consistency  of  wax, 
melting  point  60°-80°,  is  a  natural  paraffin  found  at  Boryslaw  in 
Galicia,  at  Tscheleken  near  Baku  (also  called  Neftgil),  on  the  Caspian 
Sea,  and  forms  the  ceresine  of  commerce  when  bleached.  From  it 
there  has  been  isolated  a  hydrocarbon  *'lekene"  containing  24  atoms 
of  carbon. 

Asphalt,  or  Earth  Pitch,  found  in  India,  Trinidad,  Java,  and  Cuba,  is 
a  transformation  product  of  the  higher-boiling  earth  oils,  produced  by 
the  action  of  the  oxygen  of  the  air,  just  as  paraffin  absorbs  oxygen  and 
becomes  brown  upon  prolonged  heating  in  the  air.  It  is  used  for 
cements  and  salves,  and  in  asphalting,  photo-lithography,  etc. 


B.  Olefines  or  Hydrocarbons  of  the  Ethylene  Series 
(Alkylenes) :  GJl^^. 

Summary. 


M.  Pt. 

B.  Pt. 

M.  Pt. 

B.  Pt. 

Ethylene, 
Propylene, 

Butylene  (3), 

Amylene  (5), 

Hexylene, 

Heptylene, 

Octylene, 

Nonylene, 

Decylene, 

Undecylene, 

C2H4 

C4H3|^ 

C7H14 

C'loH20 

CnH22 

-  160° 

-103° 
Gas 
-5° 

+  r 

-6° 
+  39° 
G8° 
98° 
125° 
153° 
175° 
195° 

Dodecylene, 
Tridecylene, 
Tetradecylene, 
Pentadecylene, 
Hexadecylene,  \ 
Cetene,  j 
Octadecylene, 
Eicosylene, 
Cerotene, 
Melene, 

^^12^24 
^141^28 
^16^32 

^201140 
C27H54 

-31° 
-12° 

+  4° 
18° 

58° 
62° 

\  96°+ 
233° 

{127° 
247° 

{179° 

A  Methylene,  CH^^,  does  not  exist ;  when  it  should  result, 
ethylene,  CgH^,  is  formed  instead,  (Perrot,  Butlcrow).    Thus  : 
2CH3CL  -  2IIC1  =  C^H^. 

^The  melting  and  boiling  points  given  from  C5H1Q  on,  are  those  of  the 
normal  hydrocarbons. 

+  {  Signifies  boiling  point  under  15  m.m.  pressure. 


OLEFINES. 


47 


The  inembers  of  this  second  series  of  hydrocarbons  differ  from 
tlie  paraffins  by  containing  two  atoms  of  hydrogen  less  than  these. 

In  their  physical  properties  they  resemble  the  methane 
homologues  very  closely.  C2H4,  CgH^.,  and  C4Hg  are  gases, 
C^Hjo  a  volatile  liquid,  the  higher  members  liquids  with  rising 
boiling  point  and  diminishing  mobility,  while  the  highest  are 
solid  and  similar  to  paraffins.  The  boiling  points  of  members 
of  both  series  containing  the  same  number  of  carbon  atoms, 
and  whose  constitutions  are  comparable,  lie  very  close  together, 
but  the  melting  points  of  the  olefines  are  somewhat  the  lower 
of  the  two;  e.g.  CigHg^,  M.  Pt.  21°,  B.  Pt.  {157°,  and  G^^YL^^, 
M.  Pt.  4°,  B.  Pt.  {155^ 

Most  of  the  olefines  are  easily  soluble  in  alcohol  and  ether, 
but  insoluble  in  water,  only  the  lower  members  dissolving 
slightly  in  the  latter.  The  specific  gravities  of  the  normal 
olefines,  measured  at  the  melting  points,  rise  from  about  0'63 
upwards,  and  approach  with  increasing  carbon  to  a  definite 
limit,  viz.,  about  0*79. 

In  their  chemical  relations,  the  olefines  differ  materially  from 
the  paraffins : 

(a)  By  additive  reactions.  They  combine  readily  with 
nascent  hydrogen,  with  hydrochloric,  hydrobromic,  and  hydri- 
odic  acids,  with  chlorine,  bromine,  iodine,  fuming  sulphuric 
acid,  hypochlorous  acid,  nitrous  acid,  and,  generally  speaking, 
with  two  monad  atoms  or  monovalent  groups,  whereby 
members  of  the  methane  series  or  their  derivatives  ensue; 
hence  their  name  of  "  Unsaturated  Hydrocarbons." 


Combination  with  hydrogen  is  sometimes  effected,  e.g.  in 
the  case  of  ethylene,  by  the  aid  of  platinum  black  at  the 
ordinary  temperature,  or  by  raising  to  a  red  heat,  or  by  heating 
the  olefines  or  their  di-chlor-,  etc.,  addition  products  with  fuming 
hydriodic  acid  and  phosphorus.  (Cf.  modes  of  formation  of  the 
saturated  hydrocarbons  B  1  and  5.) 


C2H4  +  H2 
C2H4  +  CI2 
C^H,  +  HI 


C2H4  +  H2SO4 


C,H,(SO,H). 


48 


I.  HYDROCARBONS. 


Ethylene  chloride,  CgH^Clg,  obtained  by  the  combination  of 
ethylene  with  chlorine,  was  formerly  called  the  oil  of  the 
Dutch  chemists,  hence  the  name  of  "  defines  "  for  the  whole 
class  of  hydrocarbons  C^jHan,  {Guthrie). 

Chlorine  adds  itself  on  more  easily  than  iodine,  but  hydro- 
chloric acid  with  more  difficulty  than  hydriodic,  bromine  and 
hydrobromic  acid  standing  mid-way. 

When  a  halogen  hydride  is  used,  the  halogen  attaches  itself 
to  that  carbon  atom  which  is  combined  with  the  least  hydro- 
gen.   (Of.  Substitution  Products.) 

Particular  olefines,  e.g.  isobutylene,  also  combine  slowly  with 
water  to  alcohols  under  the  influence  of  dilute  acids. 

Ethylene  combines  with  fuming  sulphuric  acid  at  the  ordin- 
ary temperature,  and  with  the  English  acid  at  160°-170°. 

{h)  By  their  capability  of  polymerizing,  especially  in  presence 
of  sulphuric  acid  or  zinc  chloride. 

In  this  way  are  formed  from  amylene,  C5H10,  in  presence  of  sulphuric 
acid,  the  polymers  CjoHgo,  CjgHgo,  and  C20H4Q,  and  from  butylene  similar 
compounds. 

(c)  By  their  behaviour  upon  oxidation.  They  are  easily 
oxidized  by  KMnO^  or  CrOg,  but  not  by  cold  HNO3. 

By  this  reaction,  either  oxidation  products — (acids) — containing  less 
carbon  are  formed,  by  the  breaking  up  of  the  double  carbon  bond,  (see 
p.  49,  also  A.  197,  243)  ;  or,  when  KMn04  is  employed,  no  carbon 
atoms  are  separated,  but  two  hydroxyls  are  introduced,  with  formation 
of  a  diatomic  alcohol.    (See  p.  187  ;  cf.  B.  21,  1230,  etc.) 

Modes  of  Formation,  (a)  Together  with  paraffins  by  the 
destructive  distillation  of  many  substances,  such  as  wood, 
lignite  and  coal,  and  also  by  the  distillation  of  the  paraffins 
(cf.  p.  37) ;  illuminating  gas  consequently  contains  the  olefines 
^^2^4)  CgHg,  C^Hg,  etc, 

(h)  By  abstraction  of  water  from  the  alcohols,  C^Hsn+iOH,  by 
heating  them  with  sulphuric  acid,  phosphorus  pentoxide,  zinc 
chloride,  etc.  When  sulphuric  acid  is  used,  an  alkyl-sulphuric 
acid,  e.g.  ethyl-sulphuric  acid,  CgHj^SO^H,  is  first  formed,  and 
this  decomposes  upon  further  warming  into  alkylene  and  sul- 
phuric acid.  This  method  is  especially  applicable  in  the  case 
of  the  lower  homologues.    Many  alcohols  split  up  into  olefine 


FOUMATION  ANJJ  CONSTITUTION  OF  THE  OIJ^^FINES.  41) 


and  Wiiter,  even  when  only  strongly  liciitcd  alone,  e.g.  secondary 
butyl  alcohol  at  240°. 

A  convenient  method  of  obtaining  the  higher  olefines  is  to  distil  the 
pahiiitic  ethers  of  the  higher  alcohols  under  somewhat  diminished  pres- 
sure, when  the  corresponding  olefines  and  palmitic  acid  are  produced. 

{c)  By  heating  the  halogen   compounds   C^Hsn+iX  with 
alcoholic  potash,  or  by  passing  their  vapour  over  red-hot  lime 
or  hot  oxide  of  lead,  etc.;  sometimes  by  distillation  alone  : 
+  KOH  --^  C,Hi,  +  KI  +  H,0. 
The  bromine  com])ounds  are  particularly  suited  for  this. 
{(1)  Sometimes  from  the  haloid  compounds  CuHjuXo  by  abstraction  of 
the  halogen,  e.g.  ethylene  from  ethylene  bromide  by  treatment  with 
zinc  :  C2H4Br2  +  Zn  =  C2H4  +  ZnBrg. 

(e)  By  the  electrolysis  of  dibasic  acids  of  the  succinic  acid 
series ;  thus  succinic  acid  itself  yields  ethylene  : 
C2H4(COOH)2  =         +  2CO2  +  H2. 
Other  modes  of  formation  correspond  with  these  under  D  1  and  2  for 
the  paraffins. 

Constitution  of  the  Olefines.  For  ethylene,  produced  by  the 
abstraction  of  two  atoms  of  hydrogen  from  ethane,  the  following 
formulae  may  be  given  : 

CH3  CHo —  CHo 

I.    I    •       11.    I  III.  II 

CH=  CH2—  CH2 

In  the  formulae  I.  and  II.,  two  free  carbon  affinities  are 
assumed  in  the  ethylene  molecule.  Formula  III.  follows  from 
the  assumption  that  the  affinity  which  becomes  free  at  each  of 
the  two  carbon  atoms,  upon  abstraction  of  the  hydrogen,  is 
employed  in  creating  a  "  double  bond  "  between  them. 

Upon  the  taking  up  again  of  two  atoms  of  hydrogen  or 
halogen,  the  two  free  affinities  in  I.  and  11.  would  become 
bound  by  them,  while  in  III.  the  double  bond  would  be 
changed  into  a  single  one,  and  the  free  affinity  of  either 
carbon  atom  would  be  employed  in  binding  the  two  new 
hydrogen  (or  other)  atoms. 

Now  the  ethylene  bromide  which  is  formed  by  the  addition 
of  bromine  to  ethylene  has,  for  reasons  which  will  be  given 
under  that  compound,  the  constitution  CH^Br — CH^Br,  and 

(  506 )  D 


50 


I.  HYDROCARBONS. 


likewise  the  compound  obtained  by  the  addition  of  ClOH, 
i.e.  CI  and  OH,  viz.  glycol  chlorhydrin,  the  constitution 
CHgCl — CH2OH;  consequently  formula  I.,  according  to  which 
these  substances  would  have  the  constitutions  CH3 — CHBrg 
and  CH3— CHCl(OH),  is  excluded. 

Formula  III.  is  more  probable  than  formula  II. : — 

(a)  On  account  of  methylene,  CH2=,  being  incapable  of 
existence;  all  attempts  to  isolate  it  have  only  yielded  ethylene, 
C2H4  (see  p.  46),  so  that  free  affinities  probably  cannot  exist 
in  the  carbon  atom. 

(b)  Because  one  would -otherwise  expect  to  have  two  isomeric 
ethylenes,  but  all  endeavours  to  prepare  an  isomer  have 
proved  fruitless,  (ToUens  and  L.  Meyer) ;  and  further  because 
more  isomers  of  the  next  higher  homologues,  propylene  and 
butylene,  should  exist  than  can  actually  be  prepared. 

(c)  Because  the  free  affinities  to  be  assumed  according  to  II. 
are  never  found  singly,  (which  should  in  that  case  be  possible), 
but  invariably  in  pairs  only,  and  indeed  only  on  neighbouring 
carbon  atoms.  This  is  proved  from  the  constitution  of  the 
compounds  obtained  by  the  addition,  for  instance,  of  Brg. 

It  is  therefore  to  be  concluded  that  in  ethylene  and  its 
homologues  a  double  carbon  bond,  corresponding  to  formula 
III.,  exists. 

By  this  term  double  bond"  is  not,  however,  to  be  understood  a 
closer  or  more  intimate  combination.  The  olefines,  on  the  contrary, 
are  more  readily  oxidized  than  the  paraffins,  being  thereby  attacked 
at  the  point  of  the  double  bond.  Other  properties,  especially  physical 
ones,  also  give  indications  that  a  double  bond  between  two  carbon 
atoms  is  looser,  and  therefore  more  easily  broken  than  a  single  one. 
(Of.  Briihl,  A.  211,  162).  As  soon  as  a  hydrocarbon,  CnH2n+2)  contains 
not  less  than  three  carbon  atoms,  the  elimination  of  two  atoms  of 
hydrogen,  with  formation  of  a  hydrocarbon,  On  Hon,  can  also  be  brought 
about  by  a  method  other  than  the  formation  of  a  double  bond,  viz.  by 
the  "closing  of  the  carbon  chain."  The  compounds  in  which  this  is  to 
be  assumed  are  sharply  distinguished  from  the  olefines,  and  are  not  to 
be  included  among  them. 


Ethylene,  elayl,  oil-forming  Gas,  CgH^,  =  CHg^CHg. 


KTIIYIJONE,  ETC. 


51 


This  compoiiiid  was  discovered  in  1795  by  four  Dutch  chemists.  Its 
forniuLa  wlis  established  by  JJal/ou. 

Formation — see  above,  lllnmiiiating  gas  generally  contains 
4  to  5  p.c.  of  ethylene.  The  latter  is  usually  prepared  by  heat- 
ing alcohol  with  excess  of  concentrated  sulphuric  acid,  with 
addition  of  sand,  a  mixture  of  equal  portions  of  the  two 
liquids  being  subsequently  dropped  into  the  evolution  flask. 
Sulphur  dioxide,  etc.,  are  produced  at  the  same  time  by 
secondary  reactions.  Small  quantities  can  be  conveniently 
prepared  from  ethylene  bromide  and  zinc.  It  is  further 
formed  (instead  of  its  hypothetical  isomer  indicated  above)  by 
heating  ethylidene  chloride,  CHg — CHCI2,  with  sodium. 

Liquid  at  0°  under  44  atmospheres  pressure.  B.  Pt.  103°. 
Very  slightly  soluble  in  water  and  alcohol.  Burns  with  a 
luminous  flame,  and  forms  an  explosive  mixture  with  oxygen. 
When  rapidly  mixed  with  two  volumes  of  chlorine  and 
set  fire  to,  it  burns  with  a  dark  red  flame,  with  formation  of 
hydrochloric  acid  and  deposition  of  much  soot.  It  is  con- 
verted at  a  red  heat  into  methane,  CH^,  ethane,  CgHg,  acety- 
lene, C2H2,  etc.,  with  separation  of  carbon.  (See  p.  40.)  It 
combines  with  hydrogen  in  presence  of  spongy  platinum  to 
ethane,  C^Hg. 

Propylene,  CgH^,  =  CH2=CH— CH3.  Only  one  propyl-, 
ene  belonging  to  the  olefine  group  is  theoretically  pos- 
sible and  only  one  is  known,  viz.,  a  methylated  ethylene, 
(see  p.  52.)  (On  the  assumption  of  two  free  affinities  instead 
of  a  double  bond,  four  isomeric  propylenes  would  be  possible.) 
It  can  be  prepared  from  isopropyl  iodide  and  caustic  potash, 
or  by  heating  glycerine  with  zinc  dust.  It  is  still  a  gas 
at  -  40°. 

Butylene,  C4H8.  Three  butylenes  are  possible  according  to  theory, 
and  three  are  known.  All  of  them  are  gaseous,  their  boiling  points  lying 
between  -  6°  and  + 1°.  Butylene  and  pseudo-butylene  are  derived  from 
normal  butane,  while  isobutylene  comes  from  isobutane,  since  they 
severally  combine  with  to  form  these  hydrocarbons.  The  first, 
a-butylene,  is  prepared  from  normal  ;  the  second,  /3-butylene,  from 
secondary  ;  and  the  third,  7-butylene,  from  tertiary  butyl  iodide  by 
the  action  of  caustic  potash  upon  these  ;  the  last  can  also  be  got  from 
isobutyl  alcohol  and  sulphuric  acid.    The  isomerism  of  the  two  butyl- 


52 


J.  HYDROCARBONS. 


enes  derived  from  normal  butcane  is  explained  by  the  assumption  of  a 
double  bond  at  different  points,  thus  : 

a-butylene,  CH3— CH2— CH--CH2  ;  i8-butylene,  CH3— CH^CH— CII3. 
Isobutylene  has  the  formula  (0113)2  =  C  =  CHg.  The  behaviour  of  these 
isomers  upon  oxidation  is  in  accordance  with  the  above  formulae,  the 
oxidation  always  taking  place  at  the  point  of  the  double  bond. 

Amylene,  C^H^q.  A  large  number  of  isomeric  amylenes  are 
known,  among  them  being  Iso-amylene,  obtained  from  ordinary 
amyl  iodide  and  caustic  potash,  and  for  which  the  constitutional 
formula  (CH3)2CH — CH=CH2  (isopropyl-ethylene)  is  assumed. 

The  higher  Olefines  of  normal  constitution,  with  12,  14,  16, 
.and  18  atoms  of  carbon,  have  been  prepared  by  Kmfft  accord- 
ing to  method  h. 

Cerctene  and  Melene  (M.  Pt.  60°)  are  obtained  by  the 
distillation  of  Chinese  and  bees'  wax.  They  are  like  paraffin 
in  appearance,  and  are  but  slightly  soluble  in  alcohol. 


Appendix.  For  the  hydrocarbon,  CyHg,  there  is  still 
another  constitutional  formula  possible,  viz. — 

\    /       Trimethylene  (I.). 
CH, 

CHg — CHg 

Similarly  for  C^Hg  :   |         |        Tetramethylene  (11.). 

CH2 — CH2 — CH2 
And  for  CgH^2  •   I  I       Hexamethylene  (HI.)- 

CH2 — CH2 — CH2 
The  carbon  atoms  in  these  formulae  do  not  form    open  "  but 
closed  "  chains,  or  quasi  "  rings."    There  are  many  grounds 
for  supposing  that  such  closed  chains  exist  in  certain  com- 
pounds, (see  p.  50). 

Thus,  a  gas  isomeric  with  propylene  is  known,  which  appears  to 
correspond  with  formula  L,  and  is  therefore  called  tri-methylene. 

It  is  formed  by  heating  trimethylene  bromide,  CH2Br--CH2 — CH2Br, 
with  sodium,  {Freiuid,  J.  pr.  Ch.  [2]  26,  367.)  It  combines  with 
bromine  only  with  difficulty,  but  more  easily  with  hydriodic  acid  to 
normal  propyl  iodide,  C3H7I,  and,  unlike  propylene,  it  is  not  altered 
by  KMnO^.    (See  Trimethylene  and  Tetramethylene  Derivatives.) 


53 


Fni'tlier,  a  whole  Rcrics  of  liydrocai  hoiis,  l)Oginnii\ij;  with 
C(.TIj2'  known,  which  are  obtained  by  the  achlition  of 
hydrogen  to  benzene  and  its  homologues,  eg.  hexa-liydro- 
benzene,  C^H^2-  These  do  not  belong  to  the  olcfines,  but 
most  probably  contain  closed  carbon  chains,  according  to 
formula  III.    (See  Aromatic  Hydrocarbons.) 

Identical  with  these  are — according  to  Markownihoff  and  Spady-  the 
hydrocarhons,  CuHgu,  mentioned  on  p.  45,  the  "  naphthenes, "  which 
are  contained  in  certain  petroleums  (in  the  Caucasian,  BeilsfpJn,  Kur- 
hatow,  and  in  very  small  quantity  in  the  American).  Unlike  the 
olcfmes,  these  are  not  dissolved  by  sulphuric  acid,  but  they  are  trans- 
formed .by  nitric-sulphuric  acid  or  by  heating  with  sulphur  into  deriva- 
tives of  aromatic  hydrocarbons,  or  into  the  hydrocarbons  themselves 
(see  these).  Bromine  does  not  give  addition  products  with  them,  but 
acts  as  a  substituent.  Those  already  described  are  "  Octo-naphthene," 
C'stiiS'  "  ^^^ono-naphthene,"  CgHig,  and  the  homologues  up  to  C15H3Q. 
(Cf.  B.  16,  2663;  18,  2234,  R.  662;  20,  1850). 


O.  Hydrocarbons,  C,,H2,,_2:  Acetylene  Series. 

Summary. 


B.  Pt. 

M.  Pt. 

B.  Pt. 

i 

r  Acetylene  \ 
\  (Ethine),/ 

Gas. 

^12^22 

/Dodecylidene  \ 
\    (norm.),  j 

-9° 

{]05°t 

C3H4 

Allylene  (Allene), 

r  Crotonylene,  \ 
\    etc.  (Butine),  j 

/  Valerylene,  etc.  \ 
\    (Pentine),  / 

Diallyl  (Hexine), 

51° 
/59° 

/Tetradecylidene  \ 
\    (norm.),  / 

fHexadecylidene  \ 
\  norm.)  I 
y     (Cetylene),  J 

/Octadecylidene  \ 
\    (norm.),  j 

+  6° 
20° 
30° 

{134° 
{l60° 
{l84° 

Heptine,  etc., 

108° 

Eicosylene  (norm.). 

liquid 

314° 

*  The  boiling  points  from  C4  on,  are  those  of  the  normal  compounds, 
t  Boiling  point  under  15  m.m.  pressure. 


The  hydrocarbons  of  this  series  again  differ  from  those  of  the 


54 


I.  HYDROCARBONS. 


preceding  by  containing  two  atoms  of  hydrogen  less.  In 
physical  properties  they  closely  resemble  both  the  latter  and 
those  of  the  methane  series  ;  thus  the  lowest  members  up  to 
CJIq  are  gaseous,  the  middle  ones  liquid,  and  the  highest 
solid,  and  in  their  melting  and  boiling  points  they  do  not 
differ  to  any  extent  from  those  of  the  other  series  with  an 
equal  number  of  carbon  atoms.  The  specific  gravities  of  the 
normal  hydrocarbons  C^g?  ^iv  ^i6'  ^^is'  melting 
point,  gradually  approach  with  increasing  carbon  to  a  definite 
limit  (0*80),  and  are  somewhat  higher  than  those  of  the 
corresponding  members  of  the  ethylene  series  throughout. 

In  their  chemical  relations  the  acetylenes  stand  nearer  to 
the  olefines  than  to  the  paraffins,  in  so  far  that  they  are  un- 
saturated and  therefore  capable  of  forming  addition  products. 

1.  They  combine  either  with  two  atoms  of  hydrogen  or 
halogen,  or  with  one  molecule  of  halogen  hydride  to  olefines 
or  their  substitution  products,  thus  : 

CgHg  +     =  CgH^. 

C2H2  +  HBr  =  C^HgBr  (vinyl  bromide) ; 
or  with  four  atoms  of  hydrogen  or  halogen,  or  two  molecules 
halogen  hydride  to  paraffins  or  paraffin  substitution  products, 
thus  : 

C2H2  +  =  (^2^6  (^^  presence  of  platinum  black). 

C2H2  +  2HBr--=C2H4Br2. 
C2H2  +  2Br2  =C2H2Br,. 

Like  many  of  the  olefines,  various  members  of  this  series  combine 
with  water  under  the  influence  of  dilute  acids,  thus  allylene,  C3H4, 
gives  acetone,  CsHgO ;  and  acetylene,  C2H2,  gives  crotonic  aldehyde, 
with  intermediate  formation  of  acetic  aldehyde  ;  and,  as  in  the  case  of 
the  oletines,  ether -sulphuric  acids  are  to  be  assumed  here  as  inter- 
mediate products.  HgClg  and  other  mercury  salts  also  induce  such 
hydration  : 

C2H2  +  H2O  =  C2H4O  (aldehyde). 
C3H4  +  H2O  =  CyHgO  (acetone). 

2.  The  capability  of  undergoing  polymerization   is  also 

peculiar  to  several  of  the  acetylene  hydrocarbons ;  thus, 

acetylene  is  transformed  into  benzene  upon  being  led  through 

a  red-hot  glass  tube.     This  is  an  important  synthesis  of 

benzene :  ^CgHg  =  CjjHg. 

6 


CONSTII'II'I'ION  OF  TlIK  OT.KnNKS. 


55 


At  the  same  time  the  compounds  CgH^,  C^^^Hg,  etc.,  are 
formed.  Similarly  allylcne,  C3H4,  gives  mcsitylene,  GgR^^^ 
upon  treatment  with  sulphuric  acid  and  a  little  water.  (See 
Benzene  Derivatives.) 

3.  Acetylene  and  some  of  its  homologues  react  even  at 
the  ordinary  temperature,  in  a  manner  which  is  peculiar 
to  them,  with  an  ammoniacal  solution  of  cuprous  or  argentic 
oxide,  to  form  reddish-brown  or  yellow-white  precipitates, 
e.g.  C2CU2  +  ;  CgAgg  4-  H2O,  which  are  explosive,  and 
which  are  decomposable  by  acids,  such  as  HCl,  with  regenera- 
tion of  the  hydrocarbon. 

The  hydrogen  of  acetylene  can  be  replaced  by  potassium  or 
sodium ;  thus,  upon  heating  the  former  with  sodium,  the  com- 
pounds C2HNa  and  C2Na2  are  obtained.  These  are  decom- 
posable by  water  or  acids  with  separation  of  acetylene. 

All  the  hydrocarbons  CnH2n_2  do  not,  however,  give  such 
metallic  compounds,  but  only  the  true  homologues  of  acetylene, 
i.e.  those  which  contain  a  triple  bond.    (See  below.) 

Constitution.  Upon  grounds  similar  to  those  which  have 
already  been  explained  under  ethylene,  the  constitutional 
formula  for  acetylene,  C2H2,  is  assumed  to  be  CH=CH, 
according  to  which  the  carbon  atoms  are  joined  together  by  a 
triple  bond. 

For  a  compound  C3H4,  there  are  therefore  possible  the  two 
following  constitutional  formulae  : 

CH=C— CH3  and  CH2=C=CH2. 
AUylene.  Allene. 

As  a  matter  of  fact  two  hydrocarbons  C3H4  do  exist,  only 
one  of  which,  allylene,  yields  metallic  compounds.  It  is 
therefore  to  be  considered  the  true  homologue  of  acetylene, 
containing  a  triple  bond,  according  to  the  first  of  the  two 
above  formulae,  while  to  allene  the  second  formula,  with  the 
two  double  bonds,  is  to  be  ascribed.  The  constitution  of  the 
tetra-bromo-propanes,  which  are  formed  from  these  by  the 
addition  of  Br^,  agrees  with  this  conception. 

The  capability  of  yielding  metallic  compounds  is  therefore 
contingent  upon  the  presence  of  the  group  — C=CH. 


56 


I.  HYDROCARBONS. 


In  the  case  of  the  higher  homologues  isomerism  may  be  due  cither  to 
the  difference  in  position  of  the  triple  carbon  l)ond  in  the  molecule,  or 
to  the  presence  and  different  positions  of  the  two  double  bonds.  The 
constitution  of  a  compound  is  fixed  by  the  formation  or  otherwise  of 
metallic  derivatives,  and  by  its  behaviour  upon  oxidation.  (See  Oxida- 
tion of  the  Butylenes,  p.  52. ) 

Modes  of  formation.  1.  Along  with  the  hydrocarbons 
already  described,  by  the  distillation  of  wood,  lignite,  coal, 
etc. ;  thus  illuminating  gas  contains  acetylene,  allylene,  and 
crotonylene. 

2.  By  treating  the  haloid,  preferably  the  bromine,  com- 
pounds CnHsnXg  and  GJrL^a-^^  with  alcoholic  potash  : 

C^H^Br^^C^HgBr  +  HBr. 
CsHgBr  =C2H2  +HBr. 
Further,  from  the  unsaturated  alcohols  CnHgnO.    (See  p. 
48  (b). 

3.  By  electrolysis  of  the  acids  of  the  fumaric  acid  series,  [KelcuU). 
Acetylene  is  further  formed  : 

4.  From  its  elements,  when  an  electric  arc  is  caused  to  pass 
between  two  carbon  poles  in  an  atmosphere  of  hydrogen. 

5.  By  decomposing  CgCa  or  CgKg  by  water. 

6.  By  the  incomplete  combustion  of  many  carbon  com- 
pounds, for  instance,  when  the  gas  in  a  Bunsen  lamp  burns 
below. 

7.  From  chloroform  and  sodium  (or  red-hot  copper) : 

2CECl3-f3Na2  =  CH=CH -I- 6NaCl. 

8.  From  ethane,  ethylene  and  methane  at  a  red  heat,  or  by 
the  action  of  the  induction  spark.    (See  pp.  40  and  51.) 

9.  By  heating  with  dry  potash  on  the  one  hand,  and  with  sodium 
on  the  other,  certain  acetylene  hydrocarbons  are  transformed  int  > 
isomers. 


Acetylene,  C2H2. — Was  first  obtained  impure  by  E.  Davy  horn 
CaCg  in  1839,  and  pure  by  Berthelot  in  1849.  Illuminating 
gas  contains  0*06  per  cent.  Is  best  prepared  from  ethylene 
bromide.  It  becomes  liquid  at  1°  under  a  pressure  of  48 
atmospheres,  burns  with  a  luminous  and  very  sooty  flame,  and 
has  a  peculiar  disagreeable  smell.  Dissolves  in  its  own 
volume  of  water  and  in  ^th  of  its  volume  of  alcohol.  Is 


57 


poisonous,  combining  with  the  liacnioglolnn  of  the  blood. 
It  is  decomposed  into  its  elements  with  detonation  by 
explosive  fulminate  of  silver,  and  also  by  the  electric  spark. 
It  combines  with  hydrogen  to  ethane,  upon  being  heated  with  the 
latter  in  presence  of  platinum  black,  or  to  ethylene,  upon  treating  its 
copper  compound  with  zinc  and  ammonia.  A  mixture  of  acetylene  and 
oxygen  explodes  violently  when  a  light  is  applied  to  it.  Chromic  acid 
oxidizes  acetylene  to  acetic  acid,  and  permanganate  of  potash  to  oxalic 
acid.  It  combines  with  nitrogen  under  the  influence  of  the  induction 
sp;irk  to  hydrocyanic  acid  (see  this),  and  detonates  upon  being  mixed 
with  chlorine,  but  additive  products,  e.g.  C2H2CI2,  can  however  be 
prepared.  As  little  as  -^^-^  milligramme  of  it  can  be  detected  by  the 
formation  of  the  dark-red  copper  compound  C2CU2  +  H2O,  perhaps 
CgH — Cu — Cu(OH).  This  latter  explodes  when  struck,  or  when  heated  to 
a  little  over  100°. 

AUyleiie,  C3H4,  =  CH3— C  =  CH,  can  be  prepared  from  propylene 
bromide,  CsHgBrs,  =  {CH3— CHBr-  CHsBr). 

AUene,  C3H4,  =  CH2=C=GH2,  is  obtained  by  the  electrolysis  of 
itaconic  acid. 

Crotonylene  or  Butine,  CH2=CH — CH=CH2,  is  contained  in  illumi- 
nating gas,  and  can  be  prepared  by  the  action  of  hydriodic  acid  upon 
erythrite  ;  it  is  isomeric  with 

Caoutchin  (obtained  by  the  dry  distillation  of  caoutchouc).  Pyrroly- 
lene,  C4Hg,  from  pyrrolidine,  is  probably  identical  with  the  butine  from 
erythrite.    (See  Pyrrolidine,  and  also  B.  18,  2077.) 

Piperylene,  CgHg,  =  CH2  =  CH — CHq— CH^CHg,  is  a  hydrocarbon 
obtained  from  piperidine.    (B.  16,  2059.) 

Isoprene,  Hemi-terpene,  Valerylene,  CgHg,  B.  Pt.  38°,  is  another 
hydrocarbon  closely  related  to  the  terpenes,  into  which  it  goes  by 
polymerization.    (See  limonene.) 

Di-allyl  or  Hexine,  C^E^o,  =  CH2  =  CH— CHo— CH2— CH^CH.,,  is 
got  from  allyl  iodide  and  metallic  sodium;  B.  Pt.  59  .  Has  a  penetrating 
ethereal  and  radish-like  odour.    Gives  no  metallic  compounds. 

Conylene,  C8H14,  (probably  Iso-propyl-piperylene),  B.  Pt.  125"^,  is  pre- 
pared from  Conine.    (B.  14,  710.) 

The  higher  hydrocarbons  of  this  series,  containing  12,  14,  16,  and  18 
atoms  of  carbon  in  the  molecule,  have  been  prepared  by  Krajft  from 
the  corresponding  olefines,  according  to  method  2. 

Isomeric  with  these  hydrocarbons  are  certain  hydro-derivatives  of 
aromatic  hydrocarbons,  e.g.  tetra-hydro-xylene,  C8FT14 ;  deca-hydro- 
naphthalene,  CjoHig.    (See  Aromatic  Compounds.) 

D.  Hydrocarbons,  C,,!!^,,.^  and  C^Ho,,.^. 

Among  the  hydrocarbons  still  poorer  in  hydrogen  may  be  mentioned — 


58 


II.  HALOID  SUBSTITUTION  PI101)U(JTS. 


a.  CnH2n-4:  Pirylene,  Cr^U^  (from  pipcridine.  B.  15,  1024.)  The 
homologues  of  this  have  received  the  termination  "one,"  e.g.  Hexone. 

GJI^n-e'  Di-acetylene,  C4H2,  =  CH=C— C=CH.  This 
is  prepared  by  heating  the  ammonia  salt  of  di-acetylene-di- 
carboxylic  acid,  (see  this),  with  ammoniacal  copper  solution, 
whereby  it  is  transformed  into  the  Cu-com pound  of  di- 
acetylene,  and  then  warming  this  with  potassium  cyanide.  It 
is  a  gas  of  a  peculiar  odour,  which  yields  a  violet-red  copper 
compound  and  a  yellow  silver  one,  the  latter  exploding  upon 
bein^  rubbed,  even  when  moist.    {Baeyer^  B.  18,  2269.) 

Di-propargyl,  C,H„  -  CH=C— CH^— CH^— C=CH,  is 
obtained  by  the  addition  of  bromine,  2Br2,  di-allyl,  CgH^Q,  4 
molecules  HBr  separating;  B.  Pt.  85°.  It  gives  copper  and 
silver  compounds,  and  takes  up  8  atoms  of  bromine,  etc.  It 
possesses  an  especial  interest  from  being  isomeric  with  benzene. 

Likewise  isomeric  with  the  latter  is  the  hydrocarbon 
CH3— C=G— Ce^C— CH3.    (B.  20,  R.  564). 

TropiUdene,  C7H8,  B.  Pt.  114",  from  Tropine.    (A.  217,  133.) 

II.  HALOID  SUBSTITUTION  PRODUCTS 
OF  THE  HYDROCARBONS. 

(See  p.  20  and  Table,  p.  60.) 
A.  Halogen  Derivatives  of  the  Paraffins. 

General  Properties. — Only  a  few  of  these  compounds,  e.g, 
CH3CI,  C2H5CI,  and  CHgBr  are  gaseous  at  the  ordinary  tem- 
perature, most  of  them  being  liquid,  and  those  with  a  very 
large  number  of  carbon  atoms  in  the  molecule  solid.  Such 
also  as  contain  a  large  number  of  halogen  atoms,  e.g.  CI4, 
CgClg,  are  solid  ;  among  these  come  first  the  iodine  compounds 
which,  under  similar  conditions,  also  possess  considerably 
higher  boiling  points  than  the  analogous  bromine  compounds, 
and  these  again  higher  than  the  chlorine  ones  ;  for  instance, 
C2H5I,  B.  Pt.  72^  C^H.Br,  B.  Pt.  39°,  and  C^H.Cl,  B.  Pt.  \2\ 
Under  comparable  conditions,  the  boiling  points  of  the  iodides 
lie,  for  each  atom  of  halogen,  about  50°,  (40°-60°),  and  those  of 
the  bromides  about  22°,  (20°-24°),  above  those  of  the  chlorides. 

The  lowest  members  of  the  series  have,  in  the  liquid  form, 


TT.  ITALOTD  SUr.STI'rU'l  l( )N  IMIODIKJTS. 


59 


at  first  a  higher  specific  gravity  than  water,  ejj,  Cll.jl,  Sp.  Gr. 
2-2,  C^ti'jl^'^*?  ^P-  With  increasing  carbon,  however, 

they  become  more  Hke  the  paraffins,  the  influence  of  the  halogen 
diminishing,  and  consequently  lighter  than  water. 

The  halogen  substitution  products  of  the  hydrocarbons  are 
almost  or  quite  insoluble  in  water,  but  easily  soluble  in, 
and  therefore  miscible  to  any  extent  with  alcohol  and  ether, 
and  also  soluble  in  glacial  acetic  acid.  They  often  possess  a 
sweet  ethereal  odour,  but  this  becomes  less  marked  with 
diminishing  volatility.  Most  of  them  are  combustible  ;  thus 
methyl-  and  ethyl  chloride  burn  with  a  green-bordered  flame, 
while  ethyl  iodide  and  chloroform  can  only  be  set  fire  to  with 
difficulty.  Many  members  of  the  series  containing  1  or  2 
atoms  of  carbon  produce  insensibility  and  unconsciousness 
when  inhaled,  e.g.  CHCI3,  C^HgClg,  C^H^Br,  and  C^HCl,. 

In  all  these  compounds  the  halogen  is  more  firmly  bound 
than  in  inorganic  salts,  so  that,  for  instance,  when  silver 
nitrate  is  added  to  an  alcoholic  solution  of  the  chlorine  com- 
pound, e.g.  chloroform,  it  causes  no  precipitation  of  AgCl. 
Nevertheless,  the  halogen  is  in  most  cases  easily  exchangeable 
for  other  elements  or  groups,  a  circumstance  of  the  utmost 
importance  for  many  organic  reactions.  This  is  especially 
true  for  the  iodine  and  bromine  compounds,  wliich  react  more 
readily  than  the  chlorides,  and,  on  account  of  their  lesser 
volatility,  are  easier  to  work  with ;  thus  CgH^Br  reacts  with 
AgNOg  at  the  boiling  temperature,  and  CgH^I  in  the  cold  even. 

In  all  halogen  compounds,  the  halogen  can  be  again  replaced 
by  hydrogen  by  backward  substitution,  e.g.  by  Na  amalgam, 
by  zinc  dust  and  hydrochloric  or  acetic  acid,  or  by  heating 
with  hydriodic  acid.    (See  p.  37,  B,  1.) 

Of  fluorine  compounds,  only  a  few  are  known  as  yet ;  CH3F 
and  C2H5F  are  gases. 

Modes  of  formation. — 1.  By  Substitution.  Chlorine  and 
bromine  act  for  the  most  part  as  direct  substituents,  (see 
p.  35.)  With  the  gaseous  hydrocarbons  their  action  even  in 
the  cold  is  an  extremely  energetic  one,  {e.g.  chlorine  mixed 
with  methane  easily  causes  an  explosion,  so  that  dilution  with 
COg  is  necessary) ;  the  higher  members  require  to  be  heated. 


60 


II.  ILVLOIB  SUJISTITUTJON  PRODUCTS. 


m 
O 

< 
o 
o 

p:^ 
ft 
>H 

M 
W 

H 
O 

H 

O 

P 
O 

o 

H 
H 


O 


^    .2^1    <1    .2:3    S  3 


O  OO 


pq 


p^ 


pq 


Ph 

pq 


6 
o 


.J^'  .O  S 

Q  pq  o 

Wi-H  h-i  " 
l-H  HH  O 

OOO^ 


o  S  3 2 


O  CI  Oi 


S    g  OS- 

^  ^  riO  o 

ooooo 


(M  T#  tH      (M  Ci 

(Ml-*         r-H  CO 

I 


^  p  3 

_0  ^ 

^^^^^ 

O  M  hH 

«  CO 

W  M  W 
ooo 


3 

-^^  ^ 
M  W  W 

CI  CI  c^ 
000 


— ' — ^  - 

.,  e.g, 
nary, 

itylj 

op  0 

0   Ph  ^ 

0  m  ^  >,cq  , 

isomers  of 
Normal 

iodide, 
Iso-prop^ 

isomers  of 

1.  Norma 

2.  Iso-pri 

3.  Second 

4.  Tertiai 
iodide, 

0  1 
07 

r 

0  1 

Q  I 

o 

?i 

S  ^ 
V  d  X 

O  .  CD 
M  C  M 
HH  03  l-H 

Ol-H^O 

00  o 


MODKS  OF  FORMATfON. 


6] 


The  first  halogen  atom  enters  most  easily  into  the  compound,  the 
substitution  becoming  more  diliicult  as  the  number  of  those  atoms 
present  increases.  In  the  case  of  the  higher  hydrocai'bons  there  usually 
result  two  isomeric  mono-substitution  products.  The  action  of  the 
halogens  is  further  facilitated  by  sunlight,  and  by  the  presence  of 
iodine,  this  latter  acting  as  a  carrier  of  chlorine  by  the  alternate  forma- 
tion of  ICI3  and  ICl,  thus:  IClg^ICl  +  Clg.  Antimony  pentachloride 
and  similar  chlorides  act  in  the  same  way,  and  also  ferric  chloride,  this 
last  being  eminently  suitable  for  brominating  or  iodating.  (B.  18,  2017  ; 
A.  231,  195.)  When  it  is  wanted  to  chlorinate  completely,  the  sub- 
stance in  question  is  repeatedly  saturated  with  chlorine  in  presence  of 
iodine,  and  heated  in  a  tube  to  a  high  temperature. 

From  methane  are  formed  the  whole  series  of  substitution  products 
up  to  CCI4. 

Ethane  first  yields  ethyl  chloride,  CaHgCl,  then  ethylidene  chloride, 
C2H4CI2,  and  so  on  up  to  C2CI6. 

From  propane  is  first  produced  normal  propyl  chloride,  C3H7CI,  and 
finally  CgOg.  The  latter  decomposes,  upon  vigorous  chlorination,  first 
into  CgCle  and  CCI4,  and  the  perchloro -ethane  subsequently  into  2 
molecules  CCI4.  On  chlorinating  butane  and  the  higher  hydrocarbons 
strongly,  an  analogous  splitting  up  of  the  molecule  is  effected.  CBr4 
and  other  similar  compounds  are  transformable  into  bromo -derivatives 
of  benzene. 

Iodine  seldom  acts  as  a  direct  substituent,  since  by  this 
reaction  hydriodic  acid  would  be  formed,  which  would  then 
substitute  backwards.  (See  p.  37.)  To  induce  the  action 
therefore,  the  HI  formed  must  be  removed  by  HIO3  or  HgO. 
The  iodine  substitution  products  of  the  hydrocarbons  are 
usually  prepared  indirectly,  (according  to  2  or  3). 

2.  From  Unsaturated  Hydrocarbons.  These  combine  readily 
with  halogen  or  halogen  hydride.    (See  p.  47.) 

It  stands  to  reason  that  no  methane  derivatives  can  be 
formed  in  this  way. 

Ethylene  gives  with  hydrochloric,  hydrobromic,  and  hydri- 
odic acids,  ethyl  chloride,  etc.,  i.e.  mono-substitution  products 
of  ethane;  with  chlorine,  etc.,  it  gives  di-substitution  products. 

The  compound  C2H4CI2,  obtained  by  the  action  of  chlorine, 
is  called  ethylene  chloride,  and  is  isomeric  with  the  ethylidene 
chloride  got  by  the  further  chlorination  of  C2H^C1.  (For  an 
explanation  of  this  isomerism,  see  p.  G7.) 

Propylene   combines   with   hydriodic   acid    to  isopropyl 


62 


II.  HALOID  SUBSTITUTION  PRODUCTS. 


iodide,  CyH-I,  which  is  reconverted  into  propylene  by  separa- 
tion of  HI.  But  the  same  propylene  results  from  a  compound 
isomeric  with  isopropyl  iodide,  viz.,  normal  propyl  iodide, 
(and  also,  of  course,  from  the  above  mentioned  normal  propyl 
chloride),  by  the  splitting  off  of  hydriodic  (or  hydrochloric) 
acid,  so  that  by  this  reaction  normal  propyl  iodide  can  be 
transformed  into  isopropyl  iodide.  (See  p.  65.)  From  the 
three  butylenes  there  result  similarly  two  butyl  iodides,  viz., 
secondary  and  tertiary,  which,  as  well  as  the  two  other  exist- 
ing butyl  iodides,  yield  these  butylenes  again  with  alcoholic 
potash  ;  in  this  way  the  two  last-mentioned  butyl  iodides  are 
convertible  into  their  isomers,  the  two  first,  (see  p.  66). 

A  study  of  the  constitution  of  the  compounds  formed,  shows 
that  in  these  addition  reactions  the  halogen  invariably  affixes 
itself  to  that  carbon  atom  with  which  are  combined  the 
smallest  number  of  hydrogen  atoms,  e.g, 

CH3— CH=CH2  +  HI  =  CH3— CHI— CH3, 
{not  CH3— CH2— CH2I) ; 
from  C3H^X  onwards  therefore,  there  result  only  ^'  secondary  " 
and    tertiary  "  ^  compounds. 

3.  From  Compounds  containing  oxygen. 

(a)  From  the  alcohols  C^Han+iOH.  In  these  the  OH  is  readily 
exchangeable  for  chlorine,  bromine,  or  iodine  by  the  action  of 
halogen  hydride,!  thus  : 

C2H5OH  +  HBr  =  CaH^Br  +  HgO. 

In  the  action  of  these  acids  a  state  of  equilibrium  is  reached, 
since  the  above  reaction  can  go  on  in  exactly  the  opposite 
direction ;  it  is  therefore  necessary  either  to  use  a  large  excess 
of  halogen  hydride,  (e.g.  to  saturate  with  the  gas  or  to  heat  in 
a  sealed  tube),  or  to  remove  the  water  formed,  by  sulphuric 
acid,  zinc  chloride,  etc. 

*  The  names  "primary,"  "secondary,"  and  "tertiary"  compounds 
are  founded  upon  those  of  the  alcohols— primary,  secondary,  or  tertiary 
— in  question,  from  which  they  can  be  prepared  according  to  method  3. 

t  In  such  exchange  the  halogen  takes  the  place  of  the  hydroxy],  so 
that  the  constitution  of  the  haloid  product  corresponds  with  that  of  the 
alcohol  used. 


MODES  OF  FORMATION. 


G3 


Methyl-  and  ethyl  chlorides  are  easily  prei)ared  by  distil- 
ling the  corresponding  alcohol  with  common  salt  and  snlpl)uric 
acid,  or  by  leading  hydrochloric  acid  gas  into  the  warmed 
alcohol  containing  half  its  weight  of  zinc  chloride  in  solution, 
[Groves), 

The  chlorides  of  phosphorus  are  also  applicable  for  the  sub- 
stitution of  OH  by  01,  since  they  react  in  the  same  way  with 
alcohols  as  with  water,  thus. : 

POI3  +  3HOH     =    P(OH)3  +  3H01. 
POI3  +  3O2H5OH    =    P(OH)3  +  302H50h 

Phosphorus  pentachloride  is  most  frequently  used  for  this 
purpose,  going  as  a  rule  into  the  oxychloride  : 

POI5  +  O2H5OH  =  C2H5OI  +  HOI  +  POOI3. 

Phosphorus  oxychloride  itself  is  also  sometimes  employed. 
Of  especial  importance  here  is  the  application  of  the  halogen 
compounds  of  phosphorus  in  the  production  of  bromine  and 
iodine  compounds.  The  former  need  not  be  prepared  before- 
hand, the  end  being  achieved  by  gradually  bringing  phosphorus 
and  iodine  or  bromine  together  in  presence  of  the  alcohol : 
3OH3OH  +  P  -1-  31  -  3OH3I  +  H3PO3. 

(&)  From  the  polyatomic  alcohols,  halogen  substitution  pro- 
ducts are  also  obtained,  e.g.  tri-chlorhydrin,  O3H5OI3,  from 
glycerine,  03H5(OH)3,  and  POl^;  isopropyl  iodide,  OgH^I,  or 
allyl  iodide,  O3H5I,  from  glycerine  and  HI,  i.e.  I  and  P, 
according  to  the  conditions  of  the  experiment  (see  p.  65) ; 
hexyl  iodide,  OgH^gl,  from  mannite,  0(5Hg(0H)g  and  HI,  the 
latter  acting  here  as  a  reducing  agent  also. 

(c)  From  aldehydes  and  ketones,  (see  these),  j^i-chloro-substitution 
products  result  by  the  action  of  FClg,  e.g.  ethylene  chloride,  C2H4CI2, 
from  aldehyde,  C2H4O  ;  acetone  chloride,  CgHgClg,  from  acetone 
C^H^O. 

Halogen  substitution  products  are  also  occasionally  prepared  from 
acids  by  the  exchange  of  0  and  OH  for  three  CI  atoms. 

4.  Ohlorine  and  bromine  compounds  are  frequently  formed 
from  the  corresponding  iodine  or  bromine  ones  by  driving  out 
the  weaker  halogen  from  its  combination  by  the  stronger  one, 
e.g.  isopropyl  bromide  from  the  iodide,  or  methylene  bromide 
from  methylene  iodide.    Oonversely  the  chlorine  and  bromine 


64 


II.  HALOID  SUBSTITUTION  PRODUCTS. 


compounds  may  be  transformed  into  the  iodine  ones  by  heating 
with  sodium  iodide  (in  alcoholic  solution,  see  B.  18,  519), 
potassium  iodide,  dry  calcium  iodide  (B.  16,  392),  or  with 
fuming  hydriodic  acid. 

5.  For  special  modes  of  formation,  see  the  compounds  CH3CI,  CHClo, 
and  CHI3. 


Mono-substitution  Products. 

Methyl  chloride,  CH3CI,  {Dumas  and  Feligot,  from  CH^O, 
1836).  Prepared  from  methyl  alcohol,  ZnCl2,  and  HCl  (see  p. 
62);  also  by  distilling  the  "vinasse''  of  the  sugar  manu- 
factories, and  heating  the  tri-methylamine  hydrochlorate 
obtained  to  360°,  (Vincent).  Colourless  gas  with  an  ethereal 
odour.  B.  Pt.  23°.  Slightly  soluble  in  water  (4  volumes 
in  1  volume  water),  but  more  easily  in  alcohol.  Is  used  for 
the  production  of  artificial  cold,  for  extracting  perfumes  from 
flowers,  and  for  methylating  dyes  in  the  colour  industry. 
Burns  with  a  green-bordered  flame. 

Methyl  bromide,  CHgBr,  (Bunsen,  from  cacodyl  compounds, 
1844).  Prepared  from  methyl  alcohol,  P  and  Br.  B.  Pt. 
+  4*5° ;  Sp.  Gr.  1*73  at  0° ;  has  a  pleasant  ethereal  odour  similar 
to  that  of  methyl  chloride  and  of  chloroform  and  a  burning 
taste,  and  burns  with  difficulty,  with  a  greenish-brown  flame. 

Methyl  iodide,  CH3I,  (Dumas  and  Peligot),    Prepared  from 
methyl  alcohol,  P  and  I.    B.  Pt.  44° ;  Sp.  Gr.  2-27  at  25°.  Is 
not  easily  set  fire  to.    When  it  is  heated  with  16  volumes  of 
water  to  100°,  methyl  alcohol  and  hydriodic  acid  are  pro 
duced. 

Ethyl  chloride,  G^fj\  (Basilius  Valentinus :  "  Spiritus 
salis  et  vinis,"  or  sweetened  alcohol").  Prepared  by  the 
action  of  CI  on  CgHg,  (Schorlemmer ;  cf.  p.  40).  For  Groves' 
method  (1874),  see  p.  63.  Is  formed  as  a  bye-product  in  the 
manufacture  of  chloral.  Easily  compressible  gas;  B.  Pt.  +  12°. 
Burns  with  a  green-bordered  flame.  Can  be  easily  preserved 
in  alcoholic  solution  (1  :  2). 

Ethyl  bromide,  C^H^Br,  (SeruUas,  1827).    Prepared  from 


METHYL  AND  ETHYL  CHLORIDES,  ETC. 


65 


alcohol  with  P  and  Br,  or  with  KBr  +  H2SO4.  Burns  with  a 
beautiful  green  smokeless  flame,  emitting  bromine  vapours. 

Ethyl  iodide,  C2H5I,  (Gay-LussaCj  1815).  Is  best  prepared 
from  90  per  cent,  alcohol,  P  and  1.  Colourless  liquid  with  a 
peculiar  ethereal  smell,  somewhat  resembling  that  of  leeks. 
B.  Pt.  72° ;  Sp.  Gr.  1-94.  Almost  insoluble  in  water,  but  mis- 
cible  with  alcohol  and  ether,  and  difficult  of  ignition.  Heated 
with  water  to  100°,  it  is  converted,  analogously  to  methyl 
iodide,  into  C2HgO  and  HI.  Chlorine  converts  it  into  C2H;^C1, 
and  bromine  into  C2H5Br.  When  exposed  to  light,  iodine 
separates  with  formation  of  C4H^q.  It  is  used  for  inhalation  in 
cases  of  asthma. 

Of  Propyl  chloride,  -bromide,  and  -iodide,  CgH^X,  two 
isomers  each  exist,  the  normal  propyl  and  the  isopropyl  com- 
pounds, the  former  boiling  at  a  somewhat  higher  temperature 
than  the  latter.  To  the  normal  compounds  the  constitutional 
formula  CH3 — CHg — CHgX  is  ascribed,  and  to  the  iso-com- 
pounds  the  formula  CH3 — CHX — CH3,  since  they  are  derivable 
respectively  from  normal  propyl  alcohol  and  from  isopropyl 
alcohol  or  acetone,  substances  whose  constitution  is  easily 
arrived  at. 

According  to  theory  only  these  two  cases  are  possible,  since 
propane  contains  but  two  kinds  of  hydrogen  atoms,  viz.: — (1)  six 
combined  with  the  end  carbon  atoms,  and  (2)  two  combined 
with  the  middle  ones.  For  the  transformation  of  the  normal 
into  the  iso-compounds,  see  p.  62. 

Normal  propyl  chloride,  see  p.  61,  also  table,  p.  60. 

Normal  propyl  bromide  only  goes  partially  into  isopropyl 
bromide  at  280°,  but  when  heated  with  AlgBr^  the  transfor- 
mation is  direct,  an  intermediate  Al-compound  being  formed 
[KekuUy  Schr otter). 

Isopropyl  iodide  is  prepared  from  glycerine,  phosphorus, 
and  iodine  (see  p.  63) ;  allyl  iodide  is  formed  as  intermediate 
product,  and  at  the  same  time  some  propylene  : 

C3H,(OH)3  +  SHI  =  =  C^H,!  + 1^. 

C3H5I  +  HI  =C.^,  +  \. 
C8H5l  +  2HI  =  CyHjI  +  i2. 

(600 )  E 


66 


II.  HALOID  SUBSTITUTION  PRODUCTS. 


Normal  propyl  iodide  is  got  from  the  alcohol. 

The  Butyl-haloid  compounds,  O^H^X,  are  already  known 
each  in  four  isomeric  forms,  which  in  part  differ  materially 
from  one  another  in  boiling  point,  (up  to  30°). 

As  a  matter  of  fact  four  isomers  are  theoretically  possible.  Thus  from 
normal  butane  are  derived  : 

(a)  CH3-CH2— CH2— CH2I,  and  {b)  CH3— CHg— CHI— CH3. 
Normal  butyl  iodide.  Secondary  butyl  iodide. 


In  these  hydrocarbons  also  there  are  two  kinds  of  hydrogen  atoms,  [a) 
those  connected  with  the  end,  and  {b)  those  with  the  middle  carbon  atoms. 
From  tri-methyl-methane,  CH  =  (0113)3,  are  similarly  derived 


The  constitution  of  these  four  compounds  follows,  among  other 
reasons,  from  those  of  the  four  corresponding  butyl  alcohols,  (p.  84), 
from  which  they  can  be  prepared  by  the  action  of  halogen  hydride  (HI). 

As  regards  the  transformation  of  a  into  its  isomer  b,  and  of  c  into  d, 
see  p.  62.  Isobutyl  bromide  changes  into  the  tertiary  compound  by 
simple  heating  to  230°-240°,  which  is  to  be  explained  by  the  inter- 
mediate formation  of  butylene. 

The  Isobutyl  compounds  are  the  easiest  to  prepare,  (from  isobutyl 
alcohol).  The  Tertiary  readily  react  with  HgO  to  form  the  alcohol  and 
halogen  hydride,  this  taking  place  even  in  the  cold  in  the  case  of  the 
iodide.    For  the  constitution  of  tertiary  butyl  iodide,  see  also  p.  43. 

Of  the  Isomers,  CgHi^X,  e.g.  amyl  chloride,  eight  are  theoretically 
possible.  Six  chlorides  are  actually  known.  Of  special  interest  are 
iso-amyl  chloride,  bromide,  etc.,  compounds  which  are  obtained  from 
iso-amyl  alcohol,  and  to  which  the  constitution  (CH3)2=CH — CHg  —  CH2X 
is  assigned. 

Further,  analogous  compounds  with  from  6  to  12  and  even  more,  e.g. 
16  and  30,  carbon  atoms  are  known.  A  secondary  hexyl  iodide, 
CH3 — (CH2)3 — CHI — CH3,  is  got  from  mannite  or  dulcite  with  HI  and  P. 

Cetyl  bromide  and  -iodide,  CjgHggBr  and  C16H33I,  are  liquids  which 
solidify  at  a  moderate  temperature. 


{Linnemann,) 


(c)  ^^s^cH-CH^X, 

Isobutyl  iodide. 
(Wurtz.) 


and 


2.  Di-substitution  Products. 


Methylene  chloride,  CHgClg,  Methylene  bromide,  CHgBrg, 
and  Methylene  iodide,  CH2I2,  are  colourless  liquids  which 
one  obtains  either  from  the  tri-haloid  substitution  products 


ETHYLENE  AND  ETHYLIDENE  COMPOUNDS. 


67 


by  backward  substitution,  or  from  the  mono-substitution 
products  by  the  introduction  of  more  halogen.  (See  table, 
p.  60  ) 

The  compounds  C2H4X2  are  known  in  two  isomeric  forms, 
to  which  are  assigned  the  constitutional  formulae  : 

CH^X— CH^X  and  CH3— CHX^. 

Ethylene  compounds.  Ethylidene  compounds. 

The  former  result  from  the  addition  of  halogen  to  ethylene,  or 
from  the  action  of  halogen  hydride  or  halogen  phosphorus 
upon  glycol,  C2H4(OH)2,  (see  this). 

Ethylene  chloride,  C2H4CI2,  (oil  of  the  Dutch  chemists, 
1795),  B.  Pt.  84\ 

Ethylene  bromide,  G^R^Br^,  (Balard),  is  prepared  by  lead- 
ing ethylene  into  cold  bromine,  and  has  a  pleasant  odour 
like  that  of  chloroform.  M.  Pt.  +9° ;  B.  Pt.  131° ;  Sp.  Gr. 
>  2.  CrystaUizes  in  the  cold.  Yields  glycol,  C2H4(OH)2,  upon 
prolonged  heating  with  excess  of  water  to  100°,  or  with  K2CO3. 

Ethylene  iodide,  C2H4I2,  is  solid  and  easily  decomposable. 

These  compounds  yield  acetylene  with  alcoholic  potash,  and 
are  transformed  into  glycol  by  exchanging  their  halogen 
atoms  for  hydroxyl.  Now,  from  the  relation  of  the  latter  to 
glycol  chlorhydrin  and  mono-chloracetic  acid,  it  has  the  con- 
CH2— OH 

stitution  •  ;  consequently  in  ethylene  chloride,  etc., 

CHg — OH 

the  two  halogen  atoms  are  combined  with  different  atoms  of 
carbon. 

The  following  forms  more  special  proof  of  the  above  statement : 
Ethylene  chloride  can,  by  exchange  of  CI  for  OH,  be  transformed  into 
glycol  chlorhydrin,  (which  is  also  formed  from  glycol  and  HCl),  and 
this  can  then  be  oxidized  to  mono-chloracetic  acid, 
C2H3CIO2  =  CH2CI— COOH, 
(see  this).  Since  in  the  latter  the  OH  and  CI  are  bound  to  different 
carbon  atoms,  the  same  must  be  the  case  in  glycol  chlorhydrin,  and  also, 
for  the  CI  atoms,  in  ethylene  chloride. 

The  Ethylidene  compounds  are  obtained  from  aldehyde, 
(para-aldehyde),  by  exchange  of  the  oxygen  for  halogen  by 
maans  of  phosphorus  chloride,  etc. 


68 


II.  HALOID  SUBSTITUTION  PRODUCTS. 


Ethylidene  chloride,  also  called  ethidene  chloride,  is,  how- 
ever, most  conveniently  prepared  with  phosgene,  COCI2, 
thus  : 

CH3— CHO  +  COCI2  =  CH3- CHCI2  +  CO2. 
It  is  also  formed  by  the  further  chlorination  of  C2H5CI,  and  is 
a  bye-product  in  the  manufacture  of  chloral.     Its  boiling 
point  (57°)  is  lower  than  that  of  ethylene  chloride  (84°).  It 
is  an  anaesthetic. 

Propylene  chloride,  etc.,  CgHgClg,  -Brg,  -I2,  are  likewise  known. 
They  result  partly  upon  the  addition  of  halogen  to  propylene,  and  have 
then  an  unsymmetrical  constitution,  e.g.  propylene  chloride, 
CH3— CHCl— CH2CI. 
Isomeric  with  them  are  the  symmetrically  constituted  Trimethylene 
derivatives,  of  which   tri-methylene-bromide,   CIl2Br — CHg — OHgBr, 
results  from  the  addition  of  hydrobromic  acid  to  allyl  bromide  : 
CHa^CH— CHgBr  4-  HBr    =  CHaBr— CHg— CHaBr. 

3.  Tri-substitution  Products. 

Chloroform,  CHCI3,  (Liehig  and  Soubeiran,  1831 ;  formula 
established  by  Dumas ^  1835.) 

Formation.  1.  From  methane  and  methyl  chloride,  (see 
p.  59).  2.  By  heating  alcohol  with  chloride  of  lime  and 
water.  3.  Along  with  alkaline  formate  by  warming  chloral  or 
chloral  hydrate  with  aqueous  alkali : 

CCI3— CHO  +  NaOH  =  CHCI3  +  HC02Na. 

This  last  method  of  formation  is  the  best  for  the  obtaining  of 
pure  chloroform.  Its  formation  from  alcohol  and  bleaching 
powder,  i.e.  by  the  action  of  chlorine  upon  alcohol,  may  be 
considered  to  rest  upon  the  intermediate  production  of  chloral. 

Properties.  Colourless  liquid  of  a  peculiar  ethereal  odour 
and  sweetish  taste.  Hardly  soluble  in  water.  Solid  below 
-70°.  B.  Pt.  61-2°.  Sp.  Gr.  1*527.  Dissolves  fats,  resins, 
caoutchouc,  iodine,  etc.  Is  a  most  valuable  anaesthetic, 
{Simpson,  Edinburgh,  1848). 

The  carbamine  reaction  (see  Iso-nitriles)  furnishes  a  delicate 
test  for  the  presence  of  chloroform. 


BTIOMOFOIIM  ;  lODOFOIlM. 


69 


Beactionft,  Alkaline  cliroinatc;  produces  phosgene.  Potassium  amal- 
gam induces  the  formation  of  acetylene.  Potash  decomposes  it  to 
formate  and  chloride,  thus  : 

CHCI3  +  4K0H  =  HCO2K  +  3KC1  +  B.fi. 
Ammonia  at  a  red  heat  produces  hydrocyanic  and  hydrochloric  acids: 
CHCI3  +  NH3  =:  HCN  +  3HC1. 
Bromoform,  CHBrg,  is  sometimes  present  in  commercial 
bromine. 

Iodoform,  CHI3,  (SeruUas,  1822  ;  formula  established  by 
Dumas),  is  prepared  by  warming  alcohol  with  iodine  and 
alkali  or  alkaline  carbonate  : 

C2H5OH  +      +  6K0H  =  CHI3  +  HCO2K  +  5KI  +  5H2O. 

It  can  also  be  got  in  the  same  way  from  acetone,  aldehj^de, 
lactic  acid  and,  generally,  from  compounds  which  contain  the 
group  CH3— CHOH— C,  or  OH3— CO— C,  (Lieben). 

Yellow  hexagonal  plates.  M.  Pt.  119°  Contains  only  0  25 
per  cent.  H,  which  at  first  caused  the  presence  of  the  latter 
to  be  overlooked.  Has  a  peculiar  odour,  and  is  volatile  with 
steam.    Important  antiseptic. 

Methyl- chloroform,  CH3 — CCI3.  This  compound,  the  trichloride  of 
acetic  acid,  also  acts  as  an  anaesthetic. 

Glyceryl  chloride,  t/ri-chlorhydrin,  C3H5CI3,  is  obtained 
from  glycerine  and  PCl^  (p.  63).  B.  Pt.  158°.  The  corre- 
sponding bromine  compound  is  also  known,  but  not  the  iodine 
one,  C3H5I3,  which  decomposes  in  the  nascent  state  (i.e.  when 
glycerine,  phosphorus,  and  iodine  react  together),  into  allyl 
iodide,  C3H^I,  and  I2.    (See  pp.  63  and  65.) 

4.  Hig'her  Substitution  Products. 

Carbon  tetra- chloride,  CCI4.  Can  be  prepared  from  chloroform  or 
carbon  bisulphide  and  chlorine.    Colourless  liquid.    B.  Pt.  77°. 

Carbon  tetra-bromide,  CBr4.    Plates.    Boils  without  decomposition. 

Carbon  tetra-iodide,  CI4.  Dark  red  octahedra.  Decomposes  upon 
heating. 

Per-chloro- ethane,  C^Of^.  Rhombic  plates  of  camphor-like  odour. 
Melts  and  boils  at  185". 

B. — Haloid  Derivatives  of  the  Unsaturated 
Hydrocarbons. 

These  compounds  are  obtained  either  by  partially  withdraw- 


70 


III.  MONATOMIC  ALCOHOLS. 


ing  halogen  or  halogen  hydride  from  the  halogen  derivatives 
of  the  saturated  hydrocarbons,  or  by  incompletely  saturating 
the  hydrocarbons  poorer  in  hydrogen  with  halogen  or  halogen 
hydride,  e,g, 

C^H^Brg-HBr^CgHgBr. 
C2H2     +HBr  =  C2H3Br. 

The  allyl  compounds,  C3H5X,  result  from  allyl  alcohol  and 
halogen  hydride  or  halogen-phosphorus. 

These  unsaturated  products  are  very  similar  to  the  corre- 
sponding saturated  ones,  but  they  are  of  course  capable  of 
combining  further  with  halogen  or  halogen  hydride. 

The  following  among  them  may  be  mentioned  : — 

Bromo-ethylene,  vinyl  bromide,  CgHgBr,  =  CH2=CHBr. 

Allyl  chloride,  -bromide,  and  -iodide,  GR^=GR — CH2X. 

These  are  of  importance  on  account  of  their  relation  to  the 
allyl  compounds  found  in  nature,  e.g.  oil  of  mustard  and  oil  of 
garlic.  The  iodide  is  prepared  from  glycerine,  phosphorus, 
and  iodine,  and  from  it,  by  means  of  HgCl2,  the  chloride. 

Isomeric  with  them  are  the  a-Propylene  compounds, 
CH2  =  CX — CHg, 

and  the  /^-Propylene  compounds, 

CHX  =  CH-CH3. 

Per-chloro-ethylene,  C2CI4.    Colourless  liquid.    B.  Pt.  121°. 

Mono-clilor-acetylene,  CgHCl.    Gas  which  catches  fire  spontaneously. 

Mono-"brom-acetylene,  CgHBr.  Also  a  spontaneously  inflammable 
gas,  which  burns  with  a  purple  coloured  and  exceedingly  sooty  flame. 

Halogen  compounds  which  contain  several  different  halogens  are  also 
known. 

III.  MONATOMIC  ALCOHOLS. 

As  alcohols  are  designated  those  compounds  containing 
oxygen  and  of  neutral  reaction,  which,  like  bases,  combine  with 
acids  with  the  elimination  of  water,  to  form  other  compounds 
analogous  to  salts  in  constitution,  the  latter  being  termed 

ethers  "  or  "  compound  ethers,"  thus  : 

C2H5OH  +  NO2OH  =  C2H,.(aN02)  +  H20. 

Alcohols  are  further  easily  transformable  by  oxidation  into 


IMEYSTCAL  rilOPERTIKS. 


71 


compounds  riclier  in  oxygen  or  poorer  in  hydrogen,  (aldeliydes, 
ketones,  and  acids) ;  they  do  not  undergo  sul)stitution  hy  the 
action  of  halogens,  but  oxidation,  etc.,  etc. 

According  to  theory,  the  alcohols  are  derived  from  the 
hydrocarbons  by  the  replacement  of  hydrogen  by  hydroxyl. 
(See  pp.  17  and  74.) 

Just  as  we  know  mono-  and  poly-acid  bases,  so  are  there 
mono-,  di-,  tri-,  etc.,  hydric  or  -atomic  alcohols,  according  to  the 
number  of  molecules  of  a  monobasic  acid  which  can  react 
with  one  molecule  of  the  alcohol  to  form  an  ether.  The  poly- 
atomic alcohols,  e.g.  glycol,  G^JiOll),^^  glycerine,  C3H^(0H)^, 
mannite,  CgHg(0H)(5,  etc.,  will  be  treated  of  later  on. 

The  monatomic  alcohols  are  likewise  either  saturated  or 
unsaturated,  according  to  the  hydrocarbons  from  which  tliey 
are  derived.  The  unsaturated  resemble  the  saturated  closely, 
excepting  in  that  they  are  capable  of  forming  addition  com- 
pounds. 

A.  Monatomic  Saturated  Alcohols,  C^H^n+iOH 

(See  Table,  p.  72). 

The  lowest  members  of  this  series  are  colourless  mobile 
liquids,  the  middle  ones  are  more  oily,  and  the  highest — from 
dodecyl  alcohol,  C12H25OH,  onwards — are  solid  and  like 
paraffin  in  appearance  at  the  ordinary  temperature. 
Gaseous  alcohols  are  unknown.  With  analogous  constitution 
the  boiling  point  rises  with  tolerable  regularity ;  in  the  case  of 
the  lower  members  by  about  19°,  and  higher  up  in  the  series 
by  a  smaller  number.' 

The  lowest  members  are  miscible  with  water,  but  this 
solubility  rapidly  diminishes  as  the  series  ascends ;  thus  butyl 
alcohol  requires  12  parts  and  amyl  alcohol  40  parts  of  water 
for  solution,  while  the  higher  members  are  no  longer  soluble 
in  water.  The  former  can  be  separated  or  "salted  out"  from  their 
aqueous  solution  by  the  addition  of  salts,  e,g,  KgCOg  and  CaClg. 

The  specific  gravity  is  always  <  1  The  highest  members, 
(over  Cjg),  can  only  be  distilled  undecomposed  in  a  vacuum ; 
at  the  ordinary  pressure  they  break  up  into  olefine  and  water. 


III.  MONATOMIC  ALCOHOLS. 


!>•  lO  r-H  CO  C5 
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^         '-H  «— t         (M  f-H 


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ft  P 


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PRIMARY,  SECONDARY,  ANT)  TK.RTFAUY  ALCOHOT.S.  73 


The  lowest  members  poss<'Ss  an  alcoholic  odour,  those  over  Cg, 
an  odour  of  fusel,  and  both  liave  a  burning  taste,  while  the 
highest  members  are  like  paraffin  in  appearance  and  without 
either  taste  or  smell. 

Constitution  and  Isomers;  Classification  of  the 
Alcohols. 

From  CgHgO  on,  many  of  the  alcohols  are  known  in  different 
isomeric  modifications,  thus  there  are  two  propyl,  four  butyl, 
and  seven  amyl  alcohols,  etc. 

Of  these,  some  only  are  oxidizable  to  acids,  CnHsj^Og,  contain- 
ing an  equal  number  of  carbon  atoms,  an  aldehyde,  Ci^HonO, 
being  formed  as  intermediate  product.  Such  alcohols  are  termed 
primary  alcohols,  (primary  propyl-,  butyl-,  and  isobutyl 
alcohols,  etc). 

Another  class  of  alcohols  is  not  oxidizable  to  acids  with  an 
equal  number  of  atoms  of  carbon,  but  to  ketones,  C,iH2hO,  with 
separation  of  two  atoms  of  hydrogen,  e.g.  isopropyl  alcohol 
yields  acetone,  CgHgO.  These  are  termed  secondary, 
(secondary  butyl  alcohol).  Upon  further  oxidation  the 
ketones  do  indeed  yield  acids  which,  however,  contain  not  an 
equal  but  always  a  lesser  number  of  carbon  atoms,  the  carbon 
chain  having  thus  been  broken  up. 

Lastly,  the  third  class  of  alcohols,  the  tertiary,  yield  upon 
oxidation  neither  aldehydes,  ketones  nor  acids  with  an  equal 
number  of  carbon  atoms,  but  only  ketones  or  acids  containing 
fewer  atoms  of  carbon. 

Constitution  of  the  Alcohols. — In  the  monatomic  alcoliols 
one  of  the  hydrogen  atoms  plays  a  part  different  to  that  of 
the  others  ;  thus  it  is  replaceable  by  metals,  (K  and  Na),  and 
by  acid  radicles,  and,  together  with  the  oxygen  atom,  com- 
bines with  the  hydrogen  of  a  halogen  hydride  to  form  water, 
while  the  other  hydrogen  atoms  of  the  alcohol  remain  un- 
changed. This  hydrogen  atom,  which  has  already  been 
formulated  under  the  Theory  of  Types  apart  from  the 
others,  is  called  the  "  typical  "  or  "  extra- radicle  "  hydrogen 
atom.    It  is  not  joined  directly  to  the  carbon  atom  but 


74 


HI.  MONATOMIO  ALCOHOLS. 


through  the  oxygen  one,  which  is  apparent  from  the  fact  of 
the  alcohols  being  capable  of  preparation  from  the  monohaloid 
substitution  products  of  the  saturated  hydrocarbons.  (See  p. 
75.)  This  has  been  already  gone  into  in  some  detail  for 
ethyl  alcohol  (p.  17). 

The  alcohols  therefore  contain  a  hydroxyl,  OH,  and  their 
general  constitutional  formula  is  (CnH2„+i).0H. 

According  to  theory,  this  hydroxyl  can  either  replace  an 
atom  of  hydrogen  in  a  methyl  group,  in  which  case  an  alcohol 
containing  the  group  CHgOH,  (one  carbon  atom  being  joined 
to  the  other  by  a  single  bond),  results,  e.g.  CHg— CHgOH. 
Or  it  can  replace  the  hydrogen  of  aCH2 —  group  in  a  hydro- 
carbon, so  that  the  resulting  compound  contains  the  atomic 
group  —  CH.OH,  the  carbon  atom  being  here  joined  to  two 
other  ones.  Or,  lastly,  it  is  possible  that  in  a  hydrocarbon 
with  branching  carbon  chain,  the  hydrogen  of  a  methine  group 
CH=  (p.  23)  may  be  replaced  by  hydroxyl,  when  the  result- 
ing compound  consequently  contains  the  group  =C.OH,  in 
which  one  carbon  atom  is  joined  to  other  three. 

Now,  it  is  easy  to  see  that  the  group  — H 

further  oxidation,  be  transformed  into  this  other,  — 

The  latter,  which  is  termed  carboxyl,  is  contained  in  the  acids 
C^HsiiOa,  =  Cn_iH2n_iC00H,  which  result  from  the  oxidation 
of  the  primary  alcohols.  Consequently  it  is  the  primary 
alcohols  which  contain  the  atomic  group  — CHg.OH. 

The  group  =011. OH  can  likewise  be  changed  into  =0=0, 

(i.e.  C<^Qj^  -H20^,  which  is  the  characteristic  atomic  group 

of  the  ketones,  by  oxidation.  A  further  introduction  of  0  or 
OH,  whereby  acids  containing  the  group  — CO. OH  would 
ensue,  is  not  possible  in  this  case  without  a  rupture  of  the 
carbon  chain,  since  carbon  is  tetravalent.  Since  then  it  is  the 
secondary  alcohols  which  upon  oxidation  yield  ketones,  and 
not  acids  with  an  equal  number  of  carbon  atoms,  the  group 
= CH.OH  is  characteristic  of  these. 


MK/IHODS  OF  FORMATION. 


75 


Finally,  the  atomic  group  =C.OH  already  contains  the 
maximum  of  oxygen  which  can  be  combined  with  a  carbon 
atom  already  linked  to  three  other  atoms  of  carhon.  A  com- 
pound, therefore,  in  which  this  atomic  group  is  present,  cannot 
yield  upon  oxidation  an  aldehyde,  acid,  or  ketone  with  an 
equal  number  of  carbon  atoms  in  the  molecule,  but  the  result 
of  such  oxidation  must  be  the  breaking  of  the  carbon  chain, 
and  the  formation  of  acids  or  ketones  containing  a  lesser  num- 
ber of  carbon  atoms  in  the  molecule.  This  being  the  be- 
haviour of  tertiary  alcohols,  the  group  =C.OH  is  peculiar  to 
them. 

The  existence  of  the  three  classes  of  alcohols  finds  in  this 
way  a  thoroughly  satisfactory  explanation  from  theory. 

The  secondary  and  tertiary  alcohols  were  predicted  by  Kolhe  in  1864 
from  theoretical  considerations,  (A.  132,  102). 

Among  the  isomeric  alcohols  the  primary  possess  the  highest,  and  the 
tertiary  the  lowest  boiling  points,  and  the  same  holds  good  for  their 
ethers.    The  tertiary  have  the  highest  melting  points. 

Occurrence. — Different  alcohols  are  found  in  nature  com- 
bined with  organic  acids  as  ethers  in  ethereal  oils  and  waxes ; 
e.g.  methyl-,  ethyl-,  butyl-,  hexyl-,  and  octyl-alcohols,  and  also 
those  with  16,  27,  and  30  carbon  atoms. 

/.  General  Methods  of  Formation. — 1.  By"  saponification"  of 
their  ethers  (see  these),  by  boiling  with  alkalies  or  acids  or  by 
the  action  of  superheated  steam,  thus  : 

CH3.O.C7H5O2  +  KOH  =  CH3OH  +  C7H5O2.OK 

V  ^  ^   ^ 

Salicylic  methyl  Potassium 
ether.  salicylate. 

Some  ethers,  e.g,  ethyl-sulphuric  acid,  decompose  when  simply 
warmed  with  water  : 

C2H5.O.SO3H  +  H2O  =  C2H5.OH  +  SO4H2. 

2,  From  the  halogen  compounds  C,iH2,i4.iX,  and  therefore 
indirectly  from  the  paraffins  and  olefines  (pages  59  and  Gl),  in 
which  latter  case  secondary  or  tertiary  alcohols  are  obtained  : 

a.  By  warming  these,  especially  the  iodides,  with  excess  of 


76 


III.  MONATOMIC  ALCOHOLS. 


water  to  100° ;  sometimes  by  simply  allowing  the  mixture  to 
stand,  (tertiary  iodides)  : 

CgH,!  ^-  HOH  =  C^H^.OH  +  HI. 
When  but  little  water  is  used,  a  state  of  equilibrium  is 
reached  (p.  62).     These  halogen  com])ounds  may  also  be 
termed  the  halogen-hydride  ethers  of  th-e  alcohols,  so  that, 
strictly  speaking,  the  mode  of  formation  2  is  included  in  1. 

b  Frequently  by  digesting  with  moist  silver  oxide,  (which 
acts  here  like  the  unknown  hydroxide,  AgOH),  or  by  boiling 
with  lead  oxide  and  water  : 

C^H.I  +  Ag.OH  =  C2H5.OH  +  Agl. 
c.   Upon  warming  with  silver  or  potassium  acetate,  the 
acetic  ether  of  the  alcohol  in  question  is  formed,  and  this  is 
then  saponified,  thus  : 

C^H  J  +  AgO.(C2H30)  =  C2H,.O.C,H30  +  Agl. 
C2H5O.C2H3O  +  HOK  =  C2H5.OH  +  (C2H30)OK. 

3.  By  the  fermentation  of  the  carbohydrates,  (e.g.  grape 
sugar),  the  alcohols  with  2,  3,  4,  5,  and,  under  certain  condi- 
tions, even  6  atoms  of  carbon  are  produced.  (Yeast  fermenta- 
tion.) 

3a.  From  glycerine,  by  the  schizomycetes  fermentation,  alcohols 
with  2,  3,  and  4  carbon  atoms  are  formed,  [Fitz), 

4.  On  treating  the  primary  amines  with  nitrous  acid,^  the 
nitrous  ethers  of  the  alcohols  are  got : 

C2H5NH2  +  HONO  =  C2H5.OH  +  N2  +  H2O. 

5.  From  polyatomic  alcohols  by  the  partial  action  of  halogen 
hydride  and  the  backward  substitution  of  the  resulting  com- 
po]inds,  e.g.  : 

C3H5(OH)3  -1-  2HC1  =  C3H,(0H)C1,  +  2H2O. 

Glycerine.  Di-chlorhydrin. 

C3H5(OH)Cl2  +  2H2  =  C3H7OH  +  2HC1. 

Isopropyl  alcohol. 

11.  Special  Methods  of  Formation. — 1.  Primary  alcohols  are 
obtained  from  aldehydes  by  reduction  with  sodium  amalgam 

*  For  the  sake  of  convenience,  the  formula  of  the  hypothetical  nitrous 
acid,  NO2H,  =  NO.  OH,  is  used  instead  of  N2O3  +  H2O. 


NOMKNCLATUllK  ;  BEIIAVIOUll. 


77 


and  very  dilute  sulphuric  acid,  {Wurtz)  ;  or  with  acetic  acid 
and  zinc  dust,  the  acetic  ethers  of  the  alcohols  resulting  here  : 


Similarly  from  acid  anhydrides  and  nascent  hydrogen,  or 
from  a  mixture  of  anhydride  and  acid  chloride  (see  these), 
when  the  acid  ether  of  the  alcohol  is  formed. 

Since  the  acids  can  be  sjaithetically  prepared  from  alcohols  containing 
one  atom  of  carbon  less  than  themselves,  a  means  is  thus  given  for  con- 
verting one  alcohol  into  another  higher  in  series  (Lieben  and  Rossi). 

2.  Secondary  alcohols  are  formed  by  the  action  of  nascent 
hydrogen  (sodium  amalgam)  on  the  ketones,  CnHgnO  : 


Pinacones  are  obtained  here  as  bye-products.   (See  Ketones.) 

3.  Secondary  alcohols  are  further  produced  by  the  action  of  alde- 
hydes upon  zinc-methyl  or  zinc-ethyl. 

3a.  Also  by  the  action  of  zinc-alkyl  upon  ethyl  formate. 

4.  Tertiary  alcohols  are  formed  by  the  prolonged  action  of  zinc- 
methyl  or  -ethyl  (2  mols.)  upon  acid  chlorides  in  the  cold,  and  decom- 
position of  the  resulting  product  with  water,  [BiUlerow).  When  the 
action  is  only  a  short  one,  ketones  and  not  alcohols  are  got. 

5.  Secondary  or  tertiary  alcohols  sometimes  ensue  by  the  direct 
combination  of  an  olefine  with  water,  e.g.  tertiary  butyl  alcohol, 
(0113)30.  OH,  from  isobutylene. 

The  Nomenclature  of  tlie  alcohols,  especially  of  the  second- 
ary and  tertiary,  is  based  upon  a  comparison  of  them  with 
methyl  alcohol,  also  called  carbinol. 

They  are  looked  upon  as  carbinol,  OH3.OH,  in  which  the 
three  hydrogen  atoms  are  wholly  or  partially  replaced  by 
alcohol  radicles,  thus  : 

tertiary  butyl  alcohol,  (CH,.)3C.0H,  =  tri-methyl  carbinol; 


secondary  butyl  alcohol,  CH3— CH2— CH(OH)— CH3, 
=  CH(OH)(CH3)(C2H5),  =  methyl-ethyl  carbinol. 

Behaviour  of  the  alcohols.  1.  The  typical  hydrogen  atom 
(p.  73)  is  replaceable  by  metals,  e.g.  directly  by  K  or  Na, 
with  formation  of  compounds  termed  alcoholates  ; 


C2H,0  +  H,  =  C2HoO. 


C2H5OH  +  Na  =  C^HjONa  +  H. 


Sodium  ethylate. 


78 


III.  MONATOMIC  ALCOHOLS. 


These  decompose  again  into  alcohol  and  alkali  on  addition 
of  water.    (See  p.  83.) 

Primary  and  secondar}^  but  not  tertiary,  alcohols  combine 
with  baryta  and  lime  to  alcoholates  at  130°.  Crystalline  com- 
pounds are  formed  with  calcium  chloride,  so  that  this  salt 
cannot  be  used  for  drying  the  alcohols ;  these  compounds  are 
decomposed  by  water. 

2.  They  enter  into  the  composition  of  many  compounds,  as 
alcohol  of  crystallization."    (See  pp.  79  and  83.) 

3.  They  yield  ethers  with  acids  : 

C^H^OH  +  (C,H30)0H  =  C,H,.0.(C,H30)  +  H,0. 

Acetic  acid.       Ethyl  acetate. 

4.  Dehydrating  agents  convert  them  into  olefines. 

5.  With  halogen  hydride  or  halogen  phosphorus,  mono-sub- 
stitution products  of  the  hydrocarbons  are  produced.  (See  p. 
62.) 

6.  For  the  behaviour  of  primary,  secondary,  and  tertiary 
alcohols  upon  oxidation,  see  p.  73. 

The  oxidation  of  methyl  alcohol  yields  mostly  carbonic  instead  of 
formic  acid,  on  account  of  the  easy  oxidizability  of  the  latter. 

6a.  The  higher  primary  alcohols  go  into  the  corresponding  acids  u^jon 
heating  with  soda-lime. 

7.  Halogens  do  not  substitute  but  oxidize.    (See  above.) 

8.  The  primary,  secondary,  and  tertiary  alcohols  can  also  be  distin- 
guished from  one  another  by  the  behaviour  of  their  nitro-compounds, 
which  are  formed  by  the  action  of  silver  nitrate  on  the  iodides,  ( F. 
Meyer).  They  vary  also  in  the  rate  of  rapidity  with  which  etherification 
begins,  and  the  point  at  which  it  ends,  e.g.  with  acetic  acid. 


Methyl  alcohol,  TFood  Spirit^  CH3OH.  Was  discovered 
in  wood  tar  by  Boyle  in  1661,  and  its  difference  from  ordinary 
alcohol  recognized  in  1812  by  Phillips  Taylor.  Its  composition 
was  established  in  1834  by  Dumas  and  Peligot.  Name  derived 
from  [liOv^  wine,  and  vXt],  wood. 

Occurrence.  As  salicylic  ether  in  GauUheria  procumhens  (oil 
of  winter  green,  Canada);  as  butyric  ether  in  the  unripe  seeds 
of  Heracleum  giganteum. 


METHYL  AND  ETHYL  ALCOHOLS. 


79 


Formation,  1.  By  chlorinating  methane,  CH^,  and  saponi- 
fying the  resulting  methyl  chloride,  (Berthelot), 

2.  From  methyl  iodide  and  water. 

3.  I3y  the  destructive  distillation  of  wood. 

By  this  distillation  there  are  obtained — (a)  Gases  (CH4,  CgHg,  C2H4, 
C2H2,  CgHg,  C4H8,  CO,  CO2,  H5,  etc.).  (6)  An  aqueous  distillate  of 
*' pyroligneous  acid,"  containing  methyl  alcohol,  acetic  acid,  acetone, 
methyl  acetate,  allyl  alcohol,  etc.  (c)  Wood-tar,  containing  paraffins, 
naphthalene,  phenol,  guaiacols,  etc.    {d)  Wood  charcoal. 

4.  Also  by  the  dry  distillation  of  vinasse. 

It  is  prepared  in  quantity  from  the  crude  pyroligneous  acid 
by  repeated  distillation  after  neutralization,  and  is  purified  by 
formation  of  the  CaClg  compound,  which  is  stable  at  100°,  or, 
better,  by  transformation  into  the  oxalic  or  benzoic  ether, 
both  of  which  are  easy  to  purify  and  saponify. 

Properties.  Colourless  liquid.  B.  Pt.  66°.  Sp.  Gr. 
about  0*8.  The  alcohol  of  commerce  usually  contains 
acetone.  Burns  with  a  non-luminous  flame.  Dissolves  fats, 
oils,  etc.  Acts  as  an  intoxicant  like  ethyl  alcohol  and,  like  the 
latter,  enters  into  the  composition  of  compounds  as  "  alcohol 
of  crystallization, "  e,  g.  BaO  +  2CH4O  ;  Mg{\  +  GCH^O  ; 
CaClg  +  4CH4O  (six-sided  plates).  Is  easily  oxidized  to  formic 
aldehyde  and  formic  acid,  being  also  converted  into  the  latter 
upon  heating  with  soda-lime.  Forms  with  metallic  potassium 
the  crystalline  compound  CH3OK  +  CH3OH.  Potassium 
methylate,  CH3OK,  is  a  white  crystalline  powder. 

The  anhydrous  alcohol  dissolves  a  small  amount  of  de- 
hydrated cupric  sulphate  to  a  blue-green  solution.  Distilled 
over  heated  zinc  dust,  it  decomposes  almost  quantitatively 
into  CO  +  2H2. 

Uses. — For  tar  colours— (also  as  CH3I  and  CH3CI) ;  as  methyl  ether 
in  the  manufacture  of  ice  ;  for  polishes  and  varnishes  ;  as  WiggersheMs 
preservative  liquid  ;  for  methylating  spirits  of  v^^ine,  etc. 

Ethyl  alcohol.  Spirits  of  Wine,  CgH^OH.  Liquids  con- 
taining spirits  of  wine  have  been  known  from  very  early  times,  and 
their  concentration  either  by  distillation  or  by  dehydration  with  car- 
bonate of  potash  is  also  an  old  art.  We  read  of  it  as  "  alcohol  "  in  the 
16th  century.  Lavoisier  arrived  at  the  qualitative,  and  de  Saussure  in 
1808  the  quantitative  composition  of  alcohol. 


80 


III.  MONATOMIC  ALCOHOLS. 


Occurrence.  In  the  vegetable  kingdom  alcohol  is  only  found 
occasionally,  as  butyric  ether,  but  in  the  animal  kingdom  it 
occurs  in  various  forms,  e.g,  in  diabetic  urine.  It  is  also  pre- 
sent in  small  quantity  in  coal  tar,  bone  oil,  wood  spirit,  and 
bread,  fresh  English  bread  containing  0*3  per  cent. 

Formation.  1.  From  CgHg  by  conversion  into  C2H5CI  and 
saponification  of  the  latter  according  to  modes  of  formation  1 
and  2. 

2.  From  and  cone.  H2SO4.  (See  I.,  1.)  This  method 
was  discovered  by  Faraday,  and  corroborated  in  1855  by 
Berthelot. 

3.  From  aldehyde,  C2H/3,  by  reduction.     {Wurtz,  A.  123.) 

4.  Preparation  hy  the  vinous  fermentation  of  sugar.  Directly 
from  grape  and  fruit  sugars,  CgH^gOe'  indirectly  from 
cane  sugar,  0^2^22^11'  ^^^r  previous  hydration  to  2  mole- 
cules CgH-L20g  ;  also  from  malt  sugar  (directly),  from  starch, 
etc. 

Fermentations  are  peculiar  slow  decomposition-processes  of  organic 
substances  which  go  on,  as  a  rule,  with  liberation  of  gas  and  evolution 
of  heat,  and  which  are  induced  by  micro-organisms  or  by  unorganized 
ferments.  (See  Diastase.)  Th.^  vinous  fermentation  of  sugar,  i.e.  the 
fermentation  which  produces  spirit,  is  caused  by  the  yeast  ferment, 
mycoderma  (Torula)  cerevisiae,  which  forms  rather  long  round  cells 
multiplying  l)y  germination,  and  which  exists  in  different  varieties. 
Being  a  plant,  it  requires  for  its  sustenance  inorganic  salts,  but,  as  a 
non-assimilating  fungus,  no  carbonic  acid. 

In  the  vinous  fermentation  94  to  95  per  cent,  of  the  sugar 
breaks  up  into  alcohol  and  carbonic  acid  : 

with  2*5  to  3-6  per  cent,  glycerine,  CgHgOg,  and  0*4  to  0-7  per 
cent,  succinic  acid,  C^H^O^,  as  invariable  bye-products.  In 
addition  to  these,  most  of  the  higher  homologues  of  ethyl 
alcohol  are  also  formed,  the  latter  being  classed  together  under 
the  name  of  fusel  oil. 

The  chief  constituent  of  fusel  oil  is  fermentation  amyl  alcohol  (iso- 
butyl-carbinol),  C5H11OH,  but  it  has  also  been  proved  to  contain  the 
two  propyl  alcohols,  (chiefly  iso-propyl),  normal-,  iso-,  and  tertiary- 
butyl  alcohols,  normal  and  active  amyl  (methyl-ethyl)  alcohols,  together 


ETHYL  ALCOHOL  ;  FERMENTATION. 


81 


with  higher  homologues  and  ethers.  They  can  be  separated  by  means 
of  their  hydrobromic  ethers. 

Conditions  of  fermentation.  Fermentation  can  only  go  on 
between  the  limits  of  3°  and  35°,  the  most  favourable  tempera- 
ture being  between  25°  and  30°.  It  is  also  dependent  on  the 
presence  of  a  certain  amount  of  air,  and  on  the  solution  not 
being  too  concentrated.  Yeast  loses  its  activity  upon  the 
addition  of  any  reagents  which  destroy  the  cells,  also  when  it 
is  thoroughly  dried,  when  heated  to  60°,  when  treated  with 
alcohol,  acids  and  alkalies,  and  in  the  presence  of  salicylic 
acid,  phenol,  etc. 

The  following  materials  are  used  for  the  preparation  of 
alcohol  or  of  liquids  containing  alcohol : 

(a)  Grape  sugar,  fruit  sugar,  i.e.  grapes  and  other  ripe  fruits, 
for  wine,  etc.  ;  (h)  cane  or  beet  sugar  and  molasses  for  brandy 
(see  Sugar) ;  (c)  the  starch  of  cereals  for  beer  and  corn  brandy, 
and  of  potatoes  for  potato  brandy.  The  starch  is  first  con- 
verted into  malt  sugar  and  dextrine  under  the  influence  of 
diastase,  or  into  grape  sugar,  potato  sugar,  and  dextrine  by 
boiling  with  dilute  acids,  and  these  sugars  are  then  fermented. 

A  wine  of  medium  strength  contains  to  10  per  cent,  alcohol,  port 
wine  15  per  cent.,  sherry  up  to  21  per  cent.,  champagne  8  to  9  per  cent., 
and  beer  an  average  of  2  to  6  per  cent. 

The  different  varieties  of  brandy  or  spirits  obtained  by  **  burning," 
i.e.  by  distilling  fermented  liquids,  contain  30  to  40  per  cent,  alcohol, 
and  cognac  even  over  50  per  cent. 

Purification  of  alcohol.  It  is  difficult  to  separate  alcohol 
completely  from  water  by  distillation,  since  their  boiling  points 
are  only  22°  apart  from  one  another.  Even  after  repeated 
rectification  the  distillates  are  found  to  contain  water. 

On  the  large  scale  this  separation  is  excellently  effected  by  the  use  of 
dephlegmators  and  rectifiers  or  column  apparatus,  which  are  based  upon 
the  principle  of  partial  volatilization  and  partial  cooling  of  the  vapours, 
.(Adam  and  Berard  ;  improved  hj  Savalle,  Pistorius,  Coffey,  and  others.) 
In  this  way  an  alcohol  containing  98  to  99  per  cent,  can  be  obtained. 

Aqueous  alcohol  can  be  deprived  of  the  greater  part  of 
its  water  by  the  addition  of  strongly  heated  carbonate  of 
potash  or  anhydrous  copper  sulphate,  or  by  distillation  over 

(506)  F 


82 


III.  MONATOMIC  ALCOHOLS. 


quick  lime,  and  the  last  portions  can  be  extracted  by  baryta, 
or  by  several  additions  of  metallic  sodium  and  repeated  distil- 
lation. Alcohol  containing  water  becomes  turbid  on  being 
mixed  with  benzene,  carbon  bisulphide,  or  liquid  paraffin  oil, 
and  it  gives  a  white  precipitate  of  Ba(0H)2  on  the  addition  of 
a  solution  of  BaO  in  absolute  alcohol.  Alcohol  free  from  water 
is  termed  absolute  alcohol. 

Contraction  takes  place  on  mixing  alcohol  and  water 
together,  53*9  volumes  alcohol  +  49*8  volumes  water  giving, 
not  103*7,  but  100  volumes  of  the  mixture.  The  percentage  of 
alcohol  in  any  spirit  is  determined  either  from  its  specific 
gravity  by  reference  to  a  specially  calculated  table,  or  by 
areometers  of  particular  construction,  or  by  its  vapour  tension 
as  estimated  by  Geissler's  vaporimeter. 

Properties.  Colourless  mobile  liquid  with  characteristic 
spirituous  but  not  fusel  smell.  B.  Pt.  78*3°,  or  13°  under  21 
millimetres  pressure.  Solidifies  at  - 130*5°.  Sp.  Gr.  0*79 
at  15°.  Burns  with  an  almost  non-luminous  flame.  Is 
exceedingly  hygroscopic,  and  miscible  with  water  and  with 
ether  in  all  proportions.  Forms  several  cryo-hydrates  with 
water  ( +  12Aq.,  +  3Aq.,  +  ^Aq.).  Is  an  excellent  solvent  for 
many  organic  substances  such  as  resins  and  oils,  and  also  dis- 
solves sulphur,  phosphorus,  etc.,  to  some  extent ;  consequently 
it  is  much  used  in  the  laboratory.  Gives  with  cone. 
H2SO4,  according  to  the  conditions,  ethyl-sulphuric  acid,  ether, 
or  ethylene.  For  its  behaviour  with  HCl,  etc.,  see  p.  62.  It 
diffuses  through  porous  membranes  into  a  dry  atmosphere  more 
slowly  than  water,  and  coagulates  albumen,  being  therefore 
used  for  preserving  anatomical  preparations. 

It  is  very  easily  oxidized  by  the  oxygen  of  the  air,  first  to 
aldehyde  and  then  to  acetic  acid,  either  in  presence  of  finely- 
divided  platinum  or  in  dilute  solutions  containing  nitrogenous 
matters ;  thus,  beer  and  wine  become  sour,  but  not  the  pure 
alcohol  itself.  K^Crfi^  or  Mn02  +  H2S04  oxidize  it  in  the 
first  instance  to  aldehyde  ;  fuming  nitric  acid  attacks  it 
violently  with  formation  of  nitrogen  tri-  and  tetr-oxides, 
aldehyde,  ethyl  nitrite,  and  formic,  oxalic  and  hydrocyanic 


ALCOHOL  ;  PROPYL  ALCOHOL. 


83 


acids,  but,  by  the  action  of  colourless  concentrated  HNO3, 
ethyl  nitrate  can,  without  oxidation,  be  obtained  ;  in  dilute 
solution  glycollic  acid  is  formed.  Alkalies  also  induce  a 
gradual  oxidation  in  the  air  ;  thus,  alcoholic  potash  or  soda 
solutions  quickly  become  brown  with  formation  of  aldehyde 
resin,  this  latter  resulting  from  the  action  of  the  alkali  upon 
the  aldehyde  first  produced.  Alcoholic  potash  therefore 
frequently  acts  as  a  reducing  agent,  e.g.  upon  aromatic  nitro- 
compounds. (See  these.)  Chlorine  and  bromine  first  oxidize 
alcohol  to  aldehyde  and  then  act  as  substituents.  (See  Chloral.) 
Chlorinated  alcohols  can  therefore  only  be  prepared  indirectly 
(cf.  Ethylene  chlorhydrin).  When  the  vapour  of  alcohol  is  led 
through  a  red-hot  tube,  H,  CH^,  CgH^,  C2H2,  C2Hg,  C^oHg, 
CO,  C2H4O,  C2H4O2,  etc.,  are  formed. 

Of  the  compounds  containing  alcohol  of  crystallization  may 
be  mentioned,  KOH  +  2C2HeO,  LiCl  +  4C2HeO,  CaCl2  + 
4C2H6O,  and  MgCl^  +  6C2HgO. 

Sodium  Ethylate,  C2H50Na,  is  of  special  importance  among 
the  alcoholates.  It  is  formed  by  the  action  of  sodium  upon 
absolute  alcohol.  The  crystals  of  C2H5.0Na  +  2G^qO,  at  first 
obtained,  lose  their  alcohol  of  crystallization  at  200°  and 
change  into  a  white  powder  of  CgH^ONa.  Sodium  ethylate  is 
of  especial  value  for  syntheses,  and  can  frequently  be  employed 
in  alcoholic  solution. 

When  taken  in  small  quantity  alcohol  acts  as  a  stimulant  and  an  aid 
to  digestion,  in  larger  quantity  as  an  intoxicant.  Absolute  alcohol  is 
poisonous,  and  quickly  causes  death  when  injected  into  the  veins. 

Detection  of  alcohol.  1.  By  the  iodoform  reaction  (see  Iodo- 
form), when  1  part  in  2,000  of  water  can  be  recognized. 

2.  By  means  of  benzoyl  chloride,  CgHgCOCl,  which  yields  with 
alcohol  the  characteristically-smelling  benzoic  ethyl  ether. 

Propyl  alcohols,  C3H7OH. 

1.  Normal  propyl  alcohol,  ethyl  carbinolyGR.^ — CH2 — CH2OII, 
(Chancel,  1853),  is  obtained  from  fusel  oil  by  means  of  its  hydro- 
bromic  ether  (Fittirj),  or  directly  by  fractionation.  It  has  also 
been  got  from  propionic  aldehyde  and  propionic  anhydride  by 
reduction  with  sodium  amalgam  (liossi).    It  is  a  liquid  with  a 


84 


III.  MONATOMIC  ALCOHOLS. 


pleasant  spirituous  odour,  and  boils  19°  higher  than  ethyl 
alcohol.  Miscible  with  water  in  every  proportion,  and  again 
separated  out  on  addition  of  chloride  of  calcium.  Gives  pro- 
pionic acid  upon  oxidation.  Its  constitution  follows  from  that 
of  propionic  acid,  and  from  the  preparation  of  the  latter  from 
ethyl  alcohol. 

2.  Secondary  propyl  alcohol,  isopropyl  alcohol,  or  dimethyl 
carbinol,  (CH3)2=CH.OH,  (Berthelot,  1855),  was  at  first  held  to 
be  primary.  It  is  obtained  from  isopropyl  iodide  (from 
glycerine)  by  methods  I.  2a  and  2&,  also  by  the  action  of 
sodium  amalgam  on  acetone  by  method  II.  2,  (Friedel,  1862). 
It  also  results  unexpectedly,  instead  of  the  normal  alcohol, 
from  normal  propylamine  by  method  I.  4,  on  account  of  the 
intermediate  formation  of  CgHg.  Colourless  liquid.  Boils 
about  15°  lower  than  its  isomer,  and  like  it  can  be  ^'salted 
out"  from  aqueous  solution.  Gives  acetone  upon  oxidation. 
The  constitution  of  isopropyl  alcohol  follows  from  its  formation 
from  acetone,  whose  constitution  is  CH3 — CO — CH3. 

Butyl  alcohols,  C^H^^OH.  The  four  isomers  which  are 
theoretically  possible  are  known. 

1.  Normal  butyl  alcohol,  CH3— CH2— CH2— CH^OH. 
Present  in  fusel  oil,  being  formed  especially  in  the  wine-yeast 
fermentation  (by  elliptical  yeast).  Is  got  rather  easily  from 
glycerine  by  the  schizomycetes  fermentation,  (Fitz).  Prepared 
from  butyl  aldehyde,  butyric  acid  or  butyl  chloride,  according 
to  II.  1,  {Lichen  and  Rossi,  1869).  Boils  19°  higher  than 
normal  propyl  alcohol.  Has  a  peculiar  odour,  and  gives  rise  to 
coughing  when  inhaled.  Is  not  miscible  with  water  in  all  pro- 
portions, 1  volume  requiring  12  volumes  water  for  solution  at 
the  ordinary  temperature.  Can  be  salted  out"  from  its  solu- 
tion. Gives  normal  butyric  acid,  C^HgOg,  on  oxidation.  Its 
constitution  follows  from  its  relation  to  the  acid  (see  this),  and 
from  the  preparation  of  the  acid  from  normal  propyl  alcohol. 

2.  Secondary  butyl  alcohol,  methyl-etliyl-carhinol,  or  hutyhne 
hydrate,  ^|^5\>CH0H,  =  CH— 3CH,— CH(OH)— CH3.  The  hydriodic 
ether  is  formed  from  erythiite,  C4Hg(OH)4,  and  HI  {de  Luynes),  or  from 


THE  ITJGIIKll  ALCOHOLS. 


85 


normal  biitylene  and  HI,  and  is  tlien  sai)oiiified  according  to  L  2.  Tlie 
alcohol  is  also  obtained  from  aldeliydc  and  zinc  ethyl,  according  to  IL 
8,  and  from  formic  ether  according  to  II.  4,  {Sayl7:eJ/').  Strongly 
smelling  liquid,  boiling  about  18°  lower  than  the  normal  alcohol.  Gives 
methyl-ethyl  ketone  upon  oxidation,  from  which  its  constitution  follows. 

3.  Isobutyl  alcohol,  or  fermentation  butyl  alcohol, 

is  the  most  important  of  the  butyl  alcohols.  It  is  contained 
in  fusel  oil,  (JFurtz,  1852),  especially  in  potato  fusel  oil — (beer- 
yeast  fermentation) — ,  and  is  best  isolated  from  this  as  the 
iodide.  Colourless  liquid,  with  a  spirituous  fusel  smell 
resembling  that  of  wild  jasmine.  Boils  about  8°  lower  than  the 
normal  alcohol.  Yields  isobutyric  acid,  C^HgOg,  on  oxidation, 
hence  its  constitution. 

4.  Trimethyl  carbinol,  or  tertiary  butyl  alcohol,  (0113)3  =  0.  OH, 
{Butkrow,  1863).  Is  contained  in  small  quantity  in  fusel  oil.  Prepared, 
e.g.  according  to  II.  5,  but  more  simply  by  the  action  of  75  per  cent. 
H2SO4  on  isobutylene,  from  isobutyl  alcohol.  (See  II.  5.)  Rhombic 
prisms  or  tables.  Smell  spirituous  and  resembling  that  of  camphor. 
M.  Pt.  23*5°;  B.  Pt.  33°  below  that  of  the  normal  alcohol.  Yields 
ace-tone,  acetic  acid  and  carbonic  acid  on  oxidation.  Its  consti- 
tution follows,  for  instance,  from  method  of  formation  II.  5,  and  also 
from  the  constitution  of  tertiary  butyl  iodide.    (Pp.  43  and  66.) 

Amyl  alcohols,  CgH^^OH.  Theoretically  eight  isomers  are 
possible,  four  primary,  three  secondary,  and  one  tertiary,  and 
seven  of  these  are  already  known.  cuUl.  M  ^-^--o-*^-  /sti  . 

1.  Normal  primary  amyl  alcohol, 

CH3— CH2— CH2-CH2— CH2.OH, 
is  contained  in  small  quantity  in  fusel  oil,  and  can  be  prepared 
from  normal  valeric  aldehyde,  (Liehen  and  Rossi),  and  from 
normal  pentane,  by  formation  of  C^Hj-^Cl. 

2.  Isobutyl  carbinol,  (CH3)2=CH— CH2— CH^OH,  {Erlen- 
meyer),  forms  the  chief  constituent  of  "  fermentation  amyl 
alcohol,  "which  was  already  known  to  Scheele,  and  is  also  found  in 
nature  in  Eoman  camomile  oil.    It  was  prepared  synthetically 

,from  isobutyl  alcohol  in  1876  by  the  Lieben-Eossi  method. 
M.  Pt.-134°;  B.  Pt.  13r.  Has  a  fusel  smell  and  burning 
taste,  and  is  poisonous ;  causes  the  disagreeable  toxic  after- 
effects of  intoxication  by  brandy,  etc. 


86 


III.  MONATOMTC  ALCOHOLS. 


3.  Methyl-ethyl-carbinol,  active  am/yl  alcohol,  p  t|  ">CH — 

CH2OH,  (Pasteur,  1855),  is  also  contained  in  fermentation  amyl 
alcohol.  It  turns  the  plane  of  polarization  of  light  to  the  left, 
its  chloride,  bromide,  iodide,  and  the  valeric  acid  resulting 
from  its  oxidation  being  also  optically  active  (dextro-rotatory). 

The  action  upon  polarized  light  is  connected  with  the 
presence  of  an  "asymmetric"  carbon  atom.  (See  p.  31.)  A 
dextro-rotatory  modification  of  this  alcohol,  obtained  from  it 
by  fission-fungus  fermentation  (p.  31)  exists,  its  iodide  being 
laevo-rotatory. 

Hexyl  alcohols,  Gaproyl  alcohols,  CgHjg.OH.  Of  these  seventeen  are 
possible,  and  eleven  are  already  known. 

Normal  primary  hexyl  alcohol,  obtained  from  normal  hexane  and  also 
from  caproic  acid,  CgHi.202,  is  found  in  nature  as  butyric  ether,  e.g.  in 
the  essential  oil  of  Heracleum  sphondylium.  Isomeric  with  it  is 
primary  fermentation  hexyl  alcohol  from  wine  fusel  oil. 

Heptyl  alcohols,  [Oenanthyl  alcohol),  C7H15OH  Thirty-eight  are 
possible,  and,  up  to  now,  thirteen  or  fourteen  are  known. 

Octyl  alcohols,  Q^^jOTL.  The  normal  octyl  alcohol  is  found  as  acetic 
ether,  together  with  hexyl  alcohol,  in  varieties  of  Heracleum,  etc. 

Normal  Decyl  alcohol,  CioHgiOH,  Dodecyl  alcohol,  O^^^b^H,  Tetra- 
decyl  alcohol,  C14H29OH,  Hexadecyl  alcohol,  CigHggOH,  and  Octadecyl 
alcohol,  CigHg^OH,  were  prepared  by  Krafft  in  1881,  by  reducing  the 
corresponding  acids  with  zinc  dust  and  acetic  acid.  They  are  solid  and 
like  paraffin  in  appearance. 

Normal  Hexa-decyl-alcohol,  also  called  Cetyl  alcohol,  or 

Ethal,  forms  as  palmitic  ether  the  chief  constituent  of  sper- 
maceti. The  cetyl  alcohol  of  commerce  contains,  besides,  a  homologous 
alcohol,  CigHggO. 

Ceryl  alcohol,  cerotin,  C27Hg50H,  forms  as  cerotic  ether  Chinese  wax. 

Melissic  or  Miricyl  alcohol,  CgoHgiOH  or  CgiHggOH,  is  present  as  pal- 
mitic ether  in  bees'  wax  and  in  Carnauba  wax,  and  is  most  conveniently 
prepared  from  the  latter.  The  alcohols  are  obtained  from  all  these 
ethers  (wax  varieties)  by  saponification  with  boiling  alcoholic  potash. 

B.  Monatomic  Unsaturated  Alcohols,  CnHgn^iOH. 
These  are  very  similar  to  the  saturated  alcohols  both  in 
physical  properties  and  in  general  chemical  behaviour,  but  are 
sharply  distinguished  from  the  latter  by  their  capability  of 
taking  up  2  atoms  of  halogen  or  of  hydrogen,  or  1  molecule  of 


UNSATURATED  ALCOHOLS. 


87 


halogen  hydride,  and  thereby  forming  saturated  alcohols  or 
their  mono-  or  di-haloid  substitution  products.  These  latter, 
as  already  mentioned  at  p.  78,  cannot  be  prepared  by  direct 
substitution  of  the  alcohols. 

They  thus  behave  in  this  respect  like  the  olefines,  CnHgn,  and 
so  the  existence  of  a  double  carbon  bond  must  be  assumed  in 
their  case  also.  They  are  to  be  considered  as  olefines  in  which 
an  atom  of  hydrogen  is  replaced  by  hydroxyl. 


According  to  theory,  the  existence  of  an  alcohol  with  two 
carbon  atoms,  CHg^^CH.OH,  (vinyl  alcohol),  might  be  predi- 
cated ]  this,  however,  does  not  exist  in  the  free  state  but  only 
in  its  derivatives. 

By  the  reactions  in  which  one  would  expect  it  to  be  formed,  its 
isomer,  aldehyde,  CH3.CHO  results  ;  in  fact,  the  atomic  group 
=:C=CH.OH  does  not  appear  to  be  capable  of  existence,  but  always 
goes  into  the  more  stable  one  =CH — CHO,  which  is  explicable  upon 
the  assumption  that  water,  H.OH,  is  taken  up  and  again  split  off. 
Similarly,  instead  of  the  group  CH2=(C0H) — GHg,  we  always  get  the 
other,  CH3— CO— CH3. 

Allyl  alcohol,  C3H5.OH,  =  CH2=CH— CH^OH,  {Caliours 
and  Hofmanrij  1856).  Present  to  the  extent  of  0*1  to  0*2  per 
cent,  in  wood  spirit.  Is  formed  (1)  from  allyl  iodide ;  (2)  by  re- 
duction of  its  aldehyde,  acrolein  (see  this) ;  (3)  by  heating  glyce- 
rine, C3H5(OH)3,  with  oxalic  or  formic  acid  and  some  ammonium 
chloride  to  260°.  This  last  reaction  appears  to  be  a  reduction 
process,  thus,  C3Hg03  -  -  0  =  C3HgO  ;  as  intermediate 
product,  however,  a  formic  ether  of  glycerine  (see  monoformin) 
is  obtained.  Allyl  alcohol  is  a  mobile  liquid  of  suffocating 
smell,  having  almost  the  same  boiling  point  (97°)  as  N.  propyl 
alcohol ;  like  the  latter,  it  is  miscible  with  water.  It  does  not 
take  up  nascent  hydrogen  directly,  but  chlorine,  bromine, 
cyanogen,  hypochlorous  acid,  etc.  Upon  oxidation  it  yields 
its  aldehyde,  acrolein,  and  acid,  acrylic  acid,  containing  the 
same  number  of  carbon  atoms,  and  is  therefore  a  primary 
alcohol ;  hence  the  above  constitutional  formula.  With  chromic 
acid  it  yields,  in  addition,  formic  acid. 

Several  higher  homologues  are  known. 


88  IV.  DERIVATIVES  OF  MONATOMIC  ALCOHOLS. 


0.  Monatomic  Unsaturated  Alcohols,  CJio,,_.3.0H. 

These  alcohols  are  derivatives  of  acetylene  and  its  homo- 
logues.  In  addition  therefore  to  the  general  properties  of  the 
alcohols,  and  those  common  to  the  unsaturated  alcohols  of  com- 
bining directly  with  4  atoms  of  H,  CI,  Br,  or  2  molecules  HCl, 
HBr,  etc.,  most  of  them  possess  the  further  peculiarity  of  form- 
ing explosive  compounds  v^^ith  ammoniacal  copper  and  silver 
solutions,  e.g.  C3H2AgOH,  the  former  being  coloured,  e.g. 
yellow,  and  the  latter  white ;  acids  decompose  these  com- 
pounds backwards  again.  Those  of  them  which  do  not  yield 
such  metallic  compounds  contain,  not  a  triple  bond,  but  two 
double  ones  between  the  carbon  atoms.  The  most  important 
of  the  alcohols  is 

Propargyl  alcohol,  or  proj)in?jl  alcohol, 

C3H3OH,  =  CH=C— CH2OH, 
a  mobile  liquid  of  agreeable  odour,  lighter  than  water,  and 
boiling  at  114°,  i.e.  somewhat  higher  than  normal  propyl 
alcohol.    It  takes  up  4  atoms  of  bromine. 


IV.  DERIVATIVES  OP  THE  ALCOHOLS. 

These  may  be  classed  in  the  following  divisions  : — 

1.  Ethers  of  the  alcohols,  e.g.  C2H5.O.C2H5,  ethyl  ether. 

2.  Thio-alcohols  and  ethers,  e.g.  C2H5.SH. 

3.  Compound  ethers  and  acid  derivatives  of  the  alcohols. 

4.  Nitrogen  bases  of  the  alcohol  radicles. 

5.  Other  metalloid  compounds  of  the  alcohol  radicles. 

6.  Metallic  compounds  of  the  alcohol  radicles,  or  organo- 
metallic  compounds. 

A.  Ethers  Proper,  (Alcoholic  Ethers). 

Under  ethers  of  the  monatomic  alcohols  are  understood 
compounds  of  neutral  character  derived  from  the  alcohols  by 
elimination  of  the  elements  of  water,  (1  molecule  water  from 
2  molecules  alcohol).  They  can  frequently  be  prepared  by 
treating  the  alcohols  with  sulphuric  acid,  and  are  distinguished 


ETHERS. 


89 


from  the  hitter  by  not  combining  with  acids  to  form  etliors, 
and  by  being  substituted  and  not  oxidized  by  the  halogens, 
etc.  Only  the  lowest  number  of  the  series  is  gaseous,  most  of 
them  are  liquid,  and  the  highest  are  solid.  The  more  volatile 
ethers  are  characterized  by  a  peculiar  odour  which  vanishes  as 
the  series  ascends. 

Unlike  the  alcohols,  no  one  hydrogen  atom  in  the  ethers 
plays  a  role  different  to  that  of  the  others  ;  consequently 
metallic  sodium  has  no  action  upon  them.    (See  p.  17.) 

Constitution.  The  ethers  may  be  regarded  as  the  anhy- 
drides of  the  monatomic  alcohols,  analogous  to  the  anhydrides 
of  the  mono-acid  bases  : 

For  their  re-transformation  into  alcohols,  see  below. 

They  may  also  be  considered  as  the  oxides  of  the  alcohol 
radicles,  e.g,  (02115)20,  ethyl  ether;  or,  lastly,  as  alcohols  in 
which  the  typical  hydrogen  atom  is  replaced  by  an  alcoholic 
radicle  : 

C,H,.OH     C^Hs.OCC^H^)  C2H,.0(CH3) 

Alcohol.  Ether.  Ethyl-methyl  ether. 

The  alcoholic  radicles  contained  in  them  may  either  be  the 
same,  as  in  ordinary  ether  and  in  methyl  ether,  (CH3)20,  in 
which  case  they  are  termed  simple  ethers";  or  they  may  be 
different,  as  in  methyl-ethyl  ether,  when  they  are  known  as 
"mixed"  or  'intermediate  ethers." 

The  compound  ethers  of  the  acids  are  also  frequently  termed 
"  ethers,"  e.g.  "  acetic  ether  "  =  ethyl  acetate. 

Ethers  of  tertiary  alcohols  are  not  known. 

Modes  of  formation.  1.  By  heating  the  alcohols,  CnHo„+i.OH, 
with  sulphuric  acid.  The  reaction  goes  on  in  two  phases,  e.g. 
for  ethyl  ether  thus  : 

a.  C2H5OH  +  SO4H.H  -  C,H,.(S04H)  -f  H2O. 

h.  C2H,S04H  +  C2H5.OH  =  C2H5.O.C2H,  +  H2SO4. 

In  phase  a  an  ether-sulphuric  acid  is  formed,  which,  when 
further  heated  with  alcohol,  as  in  &,  yields  ether  and  regener- 
ates sulphuric  acid.    The  latter  is  therefore  free  to  work  anew, 


90  IV.  DERIVATIVP]S  OF  MONATOMIC  ALCOHOLS. 


and  in  this  way  to  convert  a  very  large  quantity  of  alcohol 
into  ether. 

This  process  is  theoretically  a  continuous  one,  but  practically  it  has 
its  limits,  through  secondary  reactions,  such  as  the  formation  of  SOg, 
etc.  The  method  is  only  suitable  for  primary  alcohols,  secondary  and 
tertiary  going  too  easily  into  olefines.  Hydrochloric,  hydrobromic  and 
hydriodic,  among  other  acids,  act  similarly  to  sulphuric  acid  ;  thus 
ether  is  obtained  upon  heating  alcohol  with  dilute  hydrochloric  acid  in  a 
sealed  tube  to  180°,  ethyl  chloride,  C2H5CI,  being  formed  as  intermediate 
product,  and  then  reacting  to  yield  alcohol  in  a  way  analogous  to  that 
given  in  the  following  mode  of  formation.  Upon  heating  alcohol  with 
hydrochloric  acid  there  ensues,  however,  a  state  of  equilibrium  between 
the  alcohol,  ether,  ethyl  chloride,  hydrochloric  acid  and  water,  after 
which  the  same  quantity  of  each  of  these  products  is  destroyed  as  is 
formed  in  unit  of  time. 

2.  By  the  action  of  halogen-alkyl  upon  sodium-alkylate,  or 
also  upon  alcoholic  potash  : 

C2H5I  +  C2H5.0Na  =  G^li,.O.GJI^  +  Nal. 

3.  From  halogen-alkyl  and  dry  silver  oxide,  AggO,  (also  HgO  and 
NagO) : 

2C2H5I  +  Ag^O  =        0.        +  2  AgL 
Modes  of  formation  1  and  2  yield  mixed  as  well  as  simple 
ethers^  e.g.  : 

C2H5.SO4H  +  CH3.OH  =  CsH^.O.CHg  +  H2SO4. 
+  CH3.0Na  =  C5H11.O.CH3  +  Nal. 
Properties,    1.   The  ethers  are  very  stable.  Ammonia, 
alkalies,  dilute  acids,  and  metallic  sodium  have  no  action  upon 
them,  nor  has  phosphorus  pentachloride  in  the  cold. 

2.  When  superheated  with  water  in  presence  of  some  acid, 
such  as  sulphuric,  the  ethers  take  up  water  and  are  re-trans- 
formed into  alcohols,  the  secondary  more  readily  than  the 
primary. 

This  change  also  goes  on,  but  extremely  slowly,  simply  upon  standing. 

3.  Upon  warming  with  concentrated  sulphuric  acid,  alcohol  and 
ethyl-sulphuric  acid  are  formed  : 

C2H5O.  C2H5  -f  HHSO4  =  C2H5.  OH  -f  C2H5.  (SO4H). 

4.  Saturated  with  hydriodic  acid  gas  at  0°,  the  ethers  split 
up  into  alcohol  and  alkyl  iodide  : 

C2H5.O.C2H,  -f  HI  =  C2H5.OH  -f  C2H5I 

When  the  ethers  are  "  mixed,"  the  iodine  attaches  itself  to  the  radicle 
poorer  in  carbon. 


ETHYL  ETHER. 


91 


5.  When  heated  with  halogen-phosphorus,  the  oxygen  atom  is  replaced 
by  two  of  halogen,  two  molecules  of  halogen-alkyl  resulting. 

6.  Like  the  alcohols,  the  ethers  are  oxidizable,  e.g.  by  nitric 
and  chromic  acids,  but  halogens  substitute  in  them  and  do  not 
oxidize ;  in  this  latter  respect  they  resemble  the  hydrocarbons. 

Ethyl  ether,    Ether;'  {G^YL^)jd. 

Discovered  by  Valerius  Gordus  about  1544,  and  possibly  before  that 
time  by  Raymond  Ltdly.  It  was  also  called  sulphuric  ether,"  and 
"  vitriol  ether, "  on  account  of  its  being  supposed  to  contain  sulphur. 
Its  composition  was  established  by  Saussiire  in  1807,  and  Gay  Lussac 
in  1815. 

Preparation.  By  the  continuous  process  from  ethyl  alcohol 
and  sulphuric  acid  at  140°,  with  gradual  addition  of  the 
alcohol,  according  to  Boullay.  It  is  freed  from  alcohol  by 
shaking  with  water,  and  dried  by  distillation  over  lime  or 
calcium  chloride,  and  finally  over  metallic  sodium. 

Theories  of  the  formation  of  Ether.  At  first  the  action  of  the  sulphuric 
acid  was  considered  to  consist  in  an  abstraction  of  water.  Later  on,  it 
was  thought  that  the  acid  gave  rise  to  a  contact  action,  {Mitscherlich, 
Berzelius),  but  Liebig  showed  that  this  view  was  incorrect,  since  ethyl- 
sulphuric  acid  is  formed.  Liebig  assumed  that  ethyl-sulphuric  acid 
broke  up,  upon  heating,  into  ether  and  SO3,  but  Graham.,  on  the  other 
hand,  proved  that  the  acid  gives  no  ether  when  heated  alone  to  140°, 
but  only  when  heated  along  with  more  alcohol. 

4.  After  this,  Williamson  propounded  the  theory  of  etheri- 
fication  at  present  held,  a  theory  based  on  the  opinion  of 
Laurent  and  Gerhardt  that  ether  contains  two  ethyl  radicles. 
Its  correctness  was  proved  by  mode  of  formation  2,  and  also  by 
the  preparation  of  mixed  ethers. 

Properties.  Mobile  liquid  with  powerful  ethereal  odour,  very 
volatile.  M.  Pt.,  -  129° ;  B.  Pt.  -f  34°-9  ;  Sp.  Gr.  at  17°-4,  072. 
Vapour  tension  equal  to  10  atmospheres  at  1 20°.  Produces  great 
cold  on  evaporation.  Is  easily  inflammable,  and  therefore  dan- 
gerous as  a  cause  of  fire,  from  the  dissemination  of  its  very  heavy 
vapour  ;  a  mixture  of  it  with  oxygen  or  air  is  explosive.  When 
burnt  very  slowly  and  incompletely,  lampenic  acid,"  an  acid 
which  is  as  yet  but  little  known,  is  produced  with  phosphores- 
cence. It  is  somewhat  soluble  in  water  (1  part  in  10),  and,  con- 
versely, 2  volumes  of  water  dissolve  in  100  volumes  ether  j  the 


92 


IV.  DERIVATIVES  OF  MONATOMIC  ALCOHOLS. 


presence  of  water  can  be  detected  by  the  milkiness  wliich  ensues 
uj)on  the  addition  of  carbon  bisulphide.  Miscible  with  concen- 
trated hydrochloric  acid.  Ether  is  an  excellent  solvent  or  ex- 
tractive for  many  organic  substances,  and  also  for  I,  Br,  CrOg, 
Fe2Cl(3,  AuClg,  PtCl^  and  other  chlorides.  It  forms  crystalline 
compounds  with  various  substances,  e.g.  the  chlorides  and 
bromides  of  Sn,  Al,  P,  Sb,  and  Ti,  being  present  in  them  as 
ether  of  crystallization." 

When  dropped  upon  platinum  black  it  takes  fire,  and  when 
poured  into  chlorine  gas  an  explosion  results,  hydrochloric  acid 
being  set  free.  In  the  dark,  however,  and  in  the  cold,  sub- 
stitution by  chlorine  is  possible ;  the  final  product  of  the 
substitution,  perchloro  ether,  C^CI^^qO,  is  solid  and  smells 
strongly  like  camphor. 

Uses.  Ether  was  first  employed  as  an  anaesthetic  by  Simjmn 
in  1848,  but  this  property  had  been  previously  observed  by 
Faraday.  It  is  further  used  as  an  extractive  in  the  colour 
industry,  as  Hofmann's  drops  when  mixed  with  1  to  3  volumes 
of  alcohol,  for  ice  machines,  and  for  the  preparation  of  col- 
lodion, etc. 

Methyl  ether,  ( 0113)20,  {Dumas,  Peligot)^  closely  resembles  common 
ether  ;  gaseous  at  the  ordinary  temperature,  but  liquid  under  -  20°. 
It  is  prepared  on  the  large  scale  for  the  production  of  artificial  cold. 

As  regards  the  boiling  points  of  the  ethers,  the  following  law  holds 
approximately  :  the  boiling  point  —  B.  Pt.  of  the  first  constituent  alcohol 
4-B.  Pt.  of  the  second  alcohol  -120°.  Thus,  the  boiling  point  of 
(C2H5)20  =  78°4-78°-  120°  =  36°. 

Ethyl-cetyl-  and  Di-cetyl  ethers  are  solid  at  the  ordinary  temperatures. 

Several  ethers  with  unsaturated  alcohol  radicles  are  also  known, 
e.g.  Allyl  ether,  (C3H5)20,  and  Vinyl-ethyl  ether,  CgHg— 0— CgHg, 
B.Pt.  35° '5.    These  can  combine  directly  with  bromine. 

Isomers.  The  general  formula  of  the  saturated  ethers  is 
CnH2n-|-20-  To  cach  ether  there  is  therefore  a  corresponding 
saturated  alcohol  which  is  isomeric  with  it,  thus  C^HqO^ 
methyl  ether  or  ethyl  alcohol,  C^H^qO  =  di-ethyl  ether  or  butyl 
alcohol,  and  so  on.  From  C^H^oO  on,  however,  several  different 
isomeric  ethers  are  not  only  possible,  but  are  also  known,  e.g. 
di-ethyl  ether,  (€2115)20,  is  isomeric  with  methyl-propyl  ether, 
CH3.O.O3H7 ;    similarly  methyl-amyl    ether,  CH3.O.C5II1P 


ISOMERISM. 


93 


ethyl-butyl  ether,  C2H5.O.C4H9,  and  di-propyl- ether, 
C3H7.0.C3H^  are  all  isomeric.  Isomerism  of  this  kind 
depends  upon  the  fact  that  the  alcoholic  radicles — and  hydro- 
gen— are  homologous,  so  that  for  equal  sums  total  of  carbon 
atoms  the  sums  of  the  hydrogen  atoms  must  also  be  equal. 

Such  isomerism,  which  depends  upon  the  grouping  together 
by  a  polyvalent  element — in  this  case,  oxygen — of  alcohol 
radicles  which  are  individually  unequal,  but  the  sums  of  whose 
elements  taken  together  are  equal,  is  called  metamerism.  One 
of  the  alcohol  radicles  may  here  be  replaced  by  hydrogen. 

The  establishing  of  the  constitution  of  the  ethers  is  based 
upon  {a)  their  syntheses  according  to  modes  of  formation  1  or  2, 
and  {h)  their  decomposition  by  HI  according  to  p.  90. 

Alcohols  and  ethers  containing  an  equal  number  of  carbon  atoms  are 
therefore  metameric.  Alcohols  are  accordingly  compounds  which  con- 
tain hydrogen  and  one  alcohol  radicle  joined  together  by  means  of 
oxygen.  Ethers,  on  the  other  hand,  are  compounds  containing  two 
alcohol  radicles  similarly  joined. 

It  stands  to  reason,  of  course,  that  all  those  varieties  of  isomerism 
which  are  found  in  the  alcohols,  and  therefore  in  the  alcohol  radicles, 
'can  also  occur  in  the  ethers  which  contain  these  radicles. 

Varieties  of  Isomerism.  The  cases  of  isomerism  which  have 
been  mentioned  up  to  now  are  of  three  kinds.  The  first  was 
the  isomerism  of  the  higher  paraffins,  which,  since  it  is  based 
upon  the  dissimilarity  of  the  carbon  chains,  is  often  termed 
chain-isomerism.  The  isomerism  between  ethylene  and  ethy- 
lidene  chlorides  or  between  primary  and  secondary  propyl 
alcohols  depends  upon  the  differences  in  position  of  the  substi- 
tuting halogen  or  hydroxyl  in  the  same  carbon  chain,  and  is 
termed  isomerism  of  place  or  position.  In  addition  to  these 
there  is  the  third  kind,  metamerism.  Further  cases  will  be 
spoken  of  under  the  Benzene  derivatives. 

B.  Thio-alcohols  and  -ethers. 
Methyl  mercaptan,  CH^.SH,  {Dumas  and  Feligot).    B.  Pt.  6°. 
Ethyl  mercaptan,  {Zeise,  1833).    B.  Pt.  36\ 

Methyl  sulphide,  (CH.j^S,  (EegnauU).    B.  Pt.  37°. 
Ethyl  sulphide,  (CJl,j,S.    B.  Pt.  92°,  etc. 
From  the  alcohols  and  ethers  sulphur  compounds  are  derived, 


94 


IV.  DERIVATIVES  OF  MONATOMIC  ALCOHOLS. 


by  the  replacement  of  one  atom  of  oxygen  by  one  of  sulphur. 
These  are  liquids  of  a  most  unpleasant  and  piercing  odour, 
something  like  that  of  leeks  ;  they  are  nearly  insoluble  in 
water  and  the  lower  members  are  very  volatile.  The  higher 
homologues  are  not  so  soluble  in  water,  but  continue  soluble  in 
alcohol  and  ether,  and  their  smell  is  less  strong  on  account  of 
the  rise  in  the  boiling  point.    They  are  readily  inflammable. 

The  Thio-alcohols,  also  called  mercaptans  or  alkyl  sulph- 
hydrates,  e.g.  mercaptan,  CgH^.SH,  although  of  neutral 
reaction,  possess  the  chemical  characters  of  weak  acids  and  are 
capable  of  forming  salts,  the  "mercaptides,"  especially  mercury 
compounds.  The  name  mercaptan"  is  derived  from  "corpus 
mercurio  aptum."  They  are  soluble  in  a  strong  solution  of 
potash. 

The  Thio-ethers,  also  termed  alkyl  sulphides,  e.g.  ethyl 
sulphide,  (02115)28,  are  on  the  other  hand  neutral  volatile 
lio[uids  without  acid  character. 

Both  classes  of  compounds  are  derived  from  hydrogen 
sulphide  by  the  replacement  of  either  one  or  both  atoms  of 
hydrogen  by  alcohol  radicles,  just  as  alcohol  and  ether  are 
derived  from  water : 


If  only  one  of  the  atoms  in  hydrogen  sulphide  is  substituted 
by  an  alcohol  radicle,  the  remaining  atom  preserves  in  the  new 
compound  its  original  character  and  is  easily  replaceable  by 
metals.  The  mercaptans  are  therefore  monatomic  compounds 
of  faintly  acid  character. 

The  above  thio-compounds  are  not  termed  ethers  of  hydrogen 
sulphide  because  they  are  not  saponifiable. 

The  constitution  of  these  compounds  follows  at  once  from 
their  modes  of  formation. 

Formation.    The  mercaptans  result : 

1.  By  warming  halogen  alkyl  or  alkyl  sulphate  with 
potassium  sulph-hydrate  in  concentrated  alcoholic  or  aqueous 
solution  : 


C2H,Br  v  KSH  =  C^H^.SH  +  KBr. 


THIO-ALCOHOLS  AND  -ETHERS. 


95 


2.  By  heating  alcohol  with  phosphorus  sulphide,  the  oxygen 
being  thus  replaced  by  sulphur,  (Kekule). 
The  thio-ethers  are  similarly  obtained — 

1.  From  halogen  alkyl  or  alkyl  sulphate  and  .  neutral 
potassium  sulphide  : 

2C2H5.SO4K  +  K,S  =  {G^ll,).^  +  2K2SO4. 

2.  By  treating  ether  with  phosphorus  pentasulphide. 

3.  From  halogen  alkyl  and  sodium  mercaptide. 

4.  By  the  distillation  of  mercury  mercaptide,  HgS  being  formed  at  the 
same  time. 

''Mixed  sulphides,"  comparable  with  the  "mixed  ethers," 
can  also  be  prepared,  e.g.  methyl-ethyl  sulphide,  C2H5.S.CH3. 
Behaviour.    A.  The  Mercaptans. 

Sodium  and  potassium  act  upon  the  mercaptans  to  form 
sodium  and  potassium  salts,  white  crystalline  compounds, 
which  are  decomposed  by  water.  The  mercury  salts  are  got 
by  warming  an  alcoholic  solution  of  mercaptan  with  mercuric 
oxide,  e.g.  mercuric  mercaptide,  Hg(C2H5S)2,  (white  plates). 
With  mercuric  chloride  difficultly  soluble  double  comjDounds 
are  formed,  e.g.  (C2H5.S)Hg.Cl,  a  white  precipitate.  The  lead 
salts  are  mostly  yellow-coloured,  and  are  produced  upon  mixing 
alcoholic  solutions  of  mercaptan  and  lead  acetate.  The  copper 
salt  of  mercaptan  is  a  bright  yellow  precipitate. 

2.  Upon  oxidation  with  nitric  acid  the  mercaptans  are 
transformed  into  alkyl-sulphonic  acids,  thus  : 

C2H5.SH-1-  30  =  C2H5.SO3H,  (ethyl-sulphonic  acid). 

3.  The  mercaptans  in  the  form  of  sodium  salts  are  oxidized 
by  iodine  or  by  sulphuryl  chloride,  SO2CI2,  (B.  18,  3178),  and 
also  frequently  in  ammoniacal  solution  in  the  air  to  di-suV^hides^ 
e.g.  ethyl  di-sulphide,  (62115)282,  thus : 

2C2H5S.Na  + 12  -  (C2H5)2S2  +  2NaL 
These  are  disagreeably  smelling  liquids,  which  have  a  much 
higher  boiling  point  than  the  mercaptans,  are  again  reduced  by 
nascent  hydrogen,  and  yield  with  nitric  acid  di-sulph-oxides, 
e.g.  ethyl  di-sulph- oxide,  (02115)28202. 

4.  By  the  action  of  concentrated  sulphuric  acid  disulphides  result, 
and  not  compounds  analogous  to  ethyl-sulphuric  acid. 

B.  The  Thio-ethers. 


96 


IV.  DERIVATIVES  OF  MONATOMIC  ALCOHOLS. 


1.  They  yield  double  compounds  with  metallic  salts,  e.g. 
(C^,^^,HgC\^  which  can  be  crystallized  from  ether. 

2.  They  are  capable  of  combining  with  halogen  or  oxygen. 
Thus  ethyl  sulphide  forms  with  bromine  a  dibromide,  crystal- 
lizing in  yellow  octohedra  : 

(C,H,),S  +  Br,  =  (C2H5),SBr,; 
and  with  dilute  nitric  acid,  di  ethyl  sulph-oxide  : 

a  thick  liquid  soluble  in  water,  which  combines  further  with 
nitric  acid  to  the  compound,  (02115)280,  HNO3.  Concentrated 
nitric  acid  or  permanganate  of  potash  oxidizes  the  sulphides  or 
sulph-oxides  to  sulphones,  e.g.  ethyl  sulphide  to  (di)-ethyl  sul- 
phone,  (02115)2802,  and  methyl-ethyl  sulphide  to  methyl-ethyl 
sulphone,  (OH3)(02H5)S02.  The  sulphones  are  solid  well- 
characterized  compounds  which  boil  without  decomposition. 

The  sulph-oxides  are  reduced  by  nascent  hydrogen  to 
sulphides,  but  not  the  sulphones. 

3.  The  behaviour  of  the  sulphides  towards  the  halogen  alkyls 
is  of  especial  interest.  Thus  the  substances  (OH3)2S  and  OH3I 
combine  even  in  the  cold  to  the  white  crystalline  tri-methyl- 
sulphine  iodide,  (0113)381,  which  is  soluble  in  water,  and 
which  goes  back  into  its  components  upon  heating.  This 
compound  behaves  exactly  like  a  salt  of  hydriodic  acid,  and 
yields  with  silver  oxide — (but  not  with  alkali) — an  oily 
base,  tri-methyl-sulphine  hydroxide,  (0H3)38.OH,  which 
cannot  be  volatilized  without  decomposition.  This  is  as 
strong  a  base  as  caustic  potash  and  resembles  the  latter  so 
closely  that  it  absorbs  carbonic  acid,  cauterizes  the  skin,  drives 
out  ammonia,  and  gives  salts  with  acids  with  the  evolution  of 
heat,  etc.,  etc. ;  it  also  yields  salts  with  hydrogen  sulphide 
which  are  extremely  like  the  alkaline  sulphides,  e.g.  they 
dissolve  8b283,  {Oefele,  1833 ;  Cahours). 

The  compoiinds  just  described  are  of  particular  interest  with  regard 
to  the  question  of  the  valency  of  sulphur. 

Since  in  ethyl  sulphide  both  the  alcohol  radicles  are  bound  to  the 
sulphur,  this  will  also  be  the  case  in  ethyl  sulphone,  otherwise  the 
sulphones  would  manifestly  be  easily  saponifiable.  (See  P^thyl  sulphur- 
ous acid.)    Probably  the  sulphur  in  them  is  hexavalent,  corresponding 


ETHERS  OF  THE  ALCOHOLS. 


97 


with   the   formula,  ^^2g5^S^Q.    Isomers  of  the  sulph  ones,  which 

are  readily  saponifiable,  have  recently  been  prepared  [Otto,  B.  18, 
2500).  The  sulphinic  hydroxides  also  can  only  be  explained  very 
insufficiently  as  addition  compounds,  on  the  assumption  of  the  divalence 
of  sulphur.  The  formula  (0113)28  +  CH3OH  for  tri-methyl-sulphine 
hydroxide  does  not  indicate  in  the  least  the  strongly  basic  character  of 
this  substance,  since  it  is  not  explicable  why  the  mere  addition  of  the 
neutral  methyl  alcohol  to  the  equally  neutral  methyl  sulphide  should 
produce  such  an  effect.    More  probable  is  one  of  the  two  formulae — 

(CH3)3=S-(OH)  ;  or,  (CH3)3=S-(OH) ; 

.  'I  . 

even  if  they  do  not  overcome  all  the  difficulties  involved. 

With  respect  to  isomers,  the  same  general  conditions  prevail  in  the 
sulphur  as  in  the  corresponding  oxygen  compounds. 


Sulphides  of  Unsaturated  Alcohol  Radicles. 

Vinyl  Sulphide,  (02113)28.    Present  in  Allium  ursinum. 

Allyl  sulphide,  (03115)28,  {Wertheinfiy  1844),  present  in  the 
oil  of  allium  sativum — oil  of  garlic, — in  Thlapsi  arvense,  etc. 
Prepared  from  allyl  iodide  and  KgS,  {Hofmann,  Cahours). 

Analogous  selenium  and  tellurium  compounds  of  alcohol  radicles  are 
also  known.  They  are  in  part  distinguished  by  their  excessively  dis- 
agreeable, nauseous,  and  persistent  odour. 


0.  Ethers  of  the  Alcohols  with  Inorganic  Acids 
and  their  Isomers. 

The  compound  ethers  may  be  considered  as  derived  from 
the  acids,  (see  pp.  78  and  70),  by  the  exchange  of  the  replace- 
able hydrogen  of  the  latter  for  alcoholic  radicles,  just  as  salts 
result  by  exchanging  the  hydrogen  for  a  metal — 

HNO3.  KNO3.  (C2H,)N03. 

Or,  they  are  derived  from  the  alcohols  by  exchange  of  the 
alcoholic  hydrogen  atom  for  an  acid  radicle,  i.e.  for  the  acid 
residue  which  is  combined  with  OH — 

C2H5.O.H.     CA.0.(N02).  C,H,.0.(S03H). 
The  different  ways  of  writing  the  formulae  of  ethers,  such  as 
(C2H;^)N03,  C2H5.O.NO2,  etc.  are  all  equally  justifiable. 

(506)  a 


98        IV.  DERIVATIVES  OF  THE  MONATOMIC  ALCOHOLS. 

Monobasic  acids  yield  only  one  kind  of  ether,  neutral 
ethers/^  which  are  analogous  to  the  neutral  salts  of  those  acids. 

Dibasic  acids  yield  two  series  of  ethers,  (1)  acid  ethers  and 
(2)  neutral  ethers,  corresponding  respectively  with  acid  and 
neutral  salts  ;  thus,  C2H5.H.SO4  and  (02115)2 .  SO4  are  the 
acid  and  neutral  ethyl  ethers  of  sulphuric  acid.  Tribasic  acids 
yield  three  series  of  ethers,  etc. 

The  composition  of  the  compound  ethers  is  therefore  exactly  analog- 
ous to  that  of  salts,  so  that  in  the  definition  of  polybasic  acids  their 
behaviour  in  the  formation  of  ethers  may  also  be  included. 

The  neutral  ethers  are  mostly  liquids  of  neutral  reaction, 
and  often  of  very  agreeable  odour,  with  relatively  low  boiling 
points,  and  volatile,  eventually  in  a  vacuum,  without  decom- 
position. Most  of  them  are  either  almost  or  quite  insoluble 
in  water.  The  acid  ethers,  also  called  ether-acids,  on  the 
other  hand,  are  of  acid  reaction,  without  smell,  usually  very 
easily  soluble  in  water,  much  less  stable  than  the  neutral 
ethers,  and  not  volatile  without  decomposition.  They  act  as 
acids,  i.e.  form  salts  and  ethers. 

All  compound  ethers  are  characterized  by  the  property  of 
combining  with  water  and  going  back  again  into  their  com- 
ponents, i.e.  of  undergoing  "  saponification,"  when  boiled  with 
alkalies  or  acids,  or  when  heated  with  steam  to  over  100°,  e.g. 
150-1 80"^  This  sometimes  takes  place  simply  upon  mixing 
with  water  at  the  ordinary  temperature. 

General  modes  of  formaiion.  1.  The  ethers  frequently 
result  directly  from  their  components,  with  elimination  of 
water.  Such  a  reaction,  however,  is  only  possible  when  the 
water  produced  by  it  is  rendered  harmless,  e.g.  by  being 
taken  up  by  the  acid  employed,  for  instance,  concentrated 
H2SO4,  HCl,  or  HNO3 ;  otherwise  the  ether  obtained  would 
be  retransformed  into  its  alcohol. 

A  direct  formation  of  ether  does  not  proceed  quantitatively  on 
account  of  the  disturbing  effect  of  the  v^ater  produced  in  the  reaction. 
When  equivalent  proportions  of  alcohol  and  acid  are  used,  a  definite 
point  of  equilibrium  is  arrived  at  which  cannot  be  passed  even  upon 
prolonged  heating  ;  an  excess  of  acid  or  alcohol  increases  the  yield. 
The  acid  is  therefore  frequently  allowed  to  act  in  the  nascent  state,  by 
distilling  a  mixture  of  one  of  its  salts  with  concentrated  H2SO4  and  the 


NITRIC  ETHERS,  ETC. 


99 


alcohol  in  question  ;  or  a  mixture  of  the  alcohol  and  acid  is  allowed  to 
drop  into  concentrated  sulphuric  acid  heated  to  130°,  when  the  ether 
distils  over  ;  or  the  same  mixture  is  saturated  with  gaseous  hydrochloric 
acid.  This  last  method  is  very  often  followed,  the  reaction  going  partly 
according  to  mode  of  formation  3.    (Cf.  also  p.  90.) 

2.  The  alcohol  is  heated  with  the  acid  chloride,  thus  : 

SO2CI2  +  2C2H5.OH  =  SO(OC2H5)2  +  2HC1. 

3.  The  silver  salt  of  the  acid  is  heated  with  alkyl  iodide, 
this  being  a  method  generally  applicable,  although  it  often 
leads  to  isomers  of  the  expected  ether  : 

2C,RJ.  +  SO.Ag,  =  SO.iC^H,),  +  2AgI. 

Besides  the  real  acid  ethers,  there  are  also  treated  under  this  division 
several  other  classes  of  acid  derivatives  isomeric  with  them,  but  dis- 
tinguished from  them  by  not  being  saponifiable,  i.e.  by  being  more 
stable,  e.g.  nitro-compounds,  sulphonic  and  phosphinic  acids,  etc.  The 
hydrocyanic  derivatives  of  the  alcohols  will  also  be  described  here  for 
the  sake  of  convenience.  These  latter  likewise  do  not  show  the  normal 
ether-saponifiability  into  alcohol  and  acid,  but  are  broken  up  by 
saponifying  agents  in  another  direction. 

Ethers  of  Nitric  Acid. 


Methyl  Nitrate>€H3.(N03),  =  CH3.0.(N02);  colourless 
liquid,  B.  Pt.  66°. 

Ethyl  Nitrate,  or  Nitric  Ether,  C2H5.O.NO2,  (Millon). 
B.  Pt.  86°.  Mobile  liquid  of  agreeable  odour  and  sweet  taste, 
but  with  a  bitter  after-taste;  burns  with  a  white  flame.  Both 
these  ethers  are  soluble  in  water.  The  latter  is  prepared 
directly  from  its  components,  with  the  addition  of  some  urea. 

Like  all  nitric  ethers,  the  above  compounds  contain  a  large 
proportion  of  oxygen  in  a  form  in  which  it  is  readily  given 
up,  and  they  therefore  explode  upon  being  suddenly  heated 
strongly.  They  saponify  easily  upon  boiling  with  alkalies. 
Tin  and  hydrochloric  acid  reduce  them  to  hydroxylamine  : 
C2H5(N03)  +  3Sn  +  6HCl  =  C2H5OH  +  NH3O  +  SSnCl^  +  H^O. . 

Here  also  the  nitrogen  separates  from  the  alcohol  radiclgj' 
a  reaction  similar  to  saponification. 

2.  Derivatives  of  Nitrous  Acid. 

These  include  Nitrites  and  Nitro-compounds. 


100      IV.  DERIVATIVES  OF  THE  MONATOMIC  ALCOHOLS. 


a.  Ethers  of  Nitrous  Acid,  HNOg. 

These  are  obtained  by  the  action  of  nitrogen  trioxide  or  of 
potassium  nitrite  and  sulphuric  acid,  or  of  copper  and  nitric 
acid  upon  the  alcohols.  They  are  liquids  of  aromatic  odour, 
neutral  reaction  and  very  low  boiling  point,  and  are  easily 
saponifiable.  Nascent  hydrogen  also  reconverts  them  into 
alcohol,  ammonia  being  formed  at  the  same  time. 

For  constitution,  see  nitro-compounds. 

Ethyl  Nitrite,  C2H5.0.(NO),  {Kunhel,  1681).  Formerly 
called  sweet  spirits  of  wine  or  saltpetre  ether."  Mobile 
liquid  of  a  piercing  ethereal  odour,  somewhat  resembling  that 
of  Borsdorf  apples,  and  of  a  peculiar  stinging  taste.  B.  Pt. 
+ 18°.  Burns  with  a  bright  white  flame.  Its  alcoholic 
solution  is  the  officinal  "  Spiritus  aetheris  nitrosi,"  and  is 
used  as  a  taste  corrective.  Ethyl  nitrite,  as  well  as  amyl 
nitrite,  finds  application,  e.g,  in  the  preparation  of  diazo-com- 
pounds,  (see  these). 

Methyl  Nitrite,  CH3O.NO.  Gaseous. 

Amyl  Nitrite,  C5H11O.NO.  B.  Pt.  96^  Pale  yellow 
liquid.  Is  used  in  medicine ;  it  produces  expansion  of  the 
blood  vessels  and  relaxation  of  the  contractile  muscles. 
Isomeric  with  these  ethers  are 

/?.  The  Nitro-derivatives  of  the  Hydrocarlons. 

These  are  colourless  liquids  of  ethereal  odour,  almost  or 
quite  insoluble  in  water,  and  boiling  at  temperatures  up  to  100° 
higher  than  their  isomers.  Like  the  latter  they  distil  with- 
out decomposition,  and  occasionally  explode  upon  being 
quickly  heated.  They  are  fundamentally  distinguished  from 
the  nitrous  ethers  by  not  being  saponifiable,  and  by  yielding 
amido-compounds  (see  these)  on  reduction,  the  nitrogen  being 
thus  not  separated  : 

CH3.NO2  +         =  CH3.NH2  +  2H2O. 

Nitro-methane,  CH3.NO2,  {Kolle,  V.  Meyer,  1873).  B.  Pt. 
99M01°;  Sp.  Gr.  >  1. 

Nitro-ethane,  C2H5.NO2,  (V.  Meyer  and  Stuber,  1872). 
B.  Pt.  113°-114°;  the  vapour  does  not  explode  even  at  a 
much  higher  temperature.    Burns  with  a  bright  flame. 


Nri'RO-COJMroUNDS. 


101 


General  modes  of  formation,  1.  By  treating  alkyl  iodide 
with  silver  nitrite,  (F.  Meyer),  nitro-methane  alone  results, 
nitro-e thane  in  about  an  equal  proportion  with  its  isomer, 
and  the  higher  homologues  in  regularly  decreasing  amounts 
as  compared  with  those  of  their  isomers,  from  which  however 
they  are  easily  separated  by  distillation  : 

CH3I  +  AgNOg  =  CH3.NO2  +  Agl. 

2.  Nitro-methane  is  further  formed  from  mono-chloracetate  and 
nitrite  of  potassium,  by  exchange  of  CI  for  NOg  and  separation  of  CO2, 
(Kolbe), 

Mtro-compounds  do  not,  on  the  other  hand,  result  from  the  action  of 
nitric  acid  upon  the  fatty  hydrocarbons,  or  at  least  extremely  seldom. 
(Difference  from  the  aromatic  hydrocarbons.) 

The  constitution  of  the  nitro- compounds  is  arrived  at  from 
their  not  being  saponifiable,  and  from  the  fact  that  the  nitrogen 
is  not  split  off  on  their  reduction  but  remains  directly  bound 
to  the  carbon  in  the  resulting  amines,  (see  these).  Conse- 
quently the  nitrogen  in  them  must  be  directly  joined  to  the 
alcohol  radicle,  i.e.  to  the  carbon,  and  so  their  constitutional 
formula  is  R.NO2;  for  instance  : 

0 

CH3— N<  I  ,  or  CH3— N< 
0  '  0 

according  as  N  is  taken  as  tri-  or  pentavalent. 

Nitrogen  which  is  bound  directly  to  an  alcohol  radicle  is 
therefore  not  separated  by  saponifying  agents.  Since  the 
nitrogen  of  the  isomeric  nitrous  ethers,  on  the  other  hand,  is 
easily  split  off  from  the  alcohol  radicle  either  by  saponification 
or  by  reduction,  it  is  manifestly  not  directly  combined  with 
the  carbon  but  only  through  the  oxygen.  The  nitrous  ethers 
therefore  receive  the  constitutional  formula  E.O.(NO),  e.g, 

CH3— 0— N=0, 
taking  nitrogen  as  trivalent. 

From  this  follows  for  the  hypothetical  hydrated  nitrous  acid  the 
formula  H.O.N:0,  and  for  anhydride  the  formula  (NOjgO.  Simultane- 
ously we  attain  from  this  to  the  constitution  of  nitric  acid.  The 
aromatic  hydrocarbons,  e.g.  benzene,  C(5H(.,  yield  with  the  latter  nitro- 
compounds, which  will  be  treated  of  later  on,  thus  : 

CeH,.H  +  HNO3  =  C,H,.^0,  +  HA 


102      IV.  DERIVATIVES  OF  THE  MON ATOMIC  ALCOHOLS. 


Nitric  acid  therefore  contains  a  nitro-group  bound  to  hydroxyl,  cor- 
responding with  the  formula : 

H.O.NO2  =  H-O-N^^,  or  H— 0-N<^>. 

Behaviour,  1.  They  yield  amines  with  reducing  agents, 
such  as  iron  and  acetic  acid,  tin  and  hydrochloric  acid,  etc. 

2.  When  the  alcohol  which  corresponds  to  the  nitro-com- 
pound  is  a  primary  or  secondary  one,  so  that  the  carbon  atom 
which  is  joined  to  the  nitro-group  is  at  the  same  time  joined 
to  hydrogen,  as  in  the  groups  — CH2.NO2  and  =CH.N02,  this 
hydrogen  is  replaceable  by  metals,  and  consequently  such 
nitro-compounds  possess  the  characteristics  of  acids. 

For  instance,  by  the  action  of  alcoholic  soda  upon  nitro-ethane  and 
nitro-methane,  the  compounds  CH3.CHNa.NO2  and  CHgNa.NOg  are 
formed,  both  crystallizing  in  fine  needles  and  being  explosive. 

The  nitro-compounds  of  tertiary  alcohols  behave  otherwise. 
Since  they  contain  no  hydrogen  joined  to  the  carbon  atom 
which  is  bound  to  the  nitro-group,  they  have  not  an  acid 
character ;  the  acidifying  influence  of  the  nitro-group  does  not 
therefore  extend  to  those  hydrogen  atoms  which  are  joined  to 
other  carbon  atoms. 

The  hydrogen  in  the  primary  and  secondary  mono- derivatives,  which 
is  attached  to  the  same  carbon  atom  as  the  NOg-group,  can  also  be 
replaced  by  bromine.  So  long  as  hydrogen,  as  well  as  this  bromine  and 
the  nitro-group,  remains  joined  to  the  carbon  atom  in  question,  the 
compound  is  of  a  strongly  acid  character,  but  when  it  also  is  substituted 
by  bromine,  the  compound  becomes  neutral;  e.g.  dibromo-nitro-ethane, 
CH3.CBr2.NO2,  is  neutral. 

3.  The  primary  nitro-compounds  yield  with  concentrated  hydrochloric 
acid  at  140°,  acids  of  the  acetic  series  containing  an  equal  number  of 
carbon  atoms,  and  hydroxylamine. 

4.  The  behaviour  of  the  nitro-alkyls  to  nitrous  acid  is  very  varied. 
The  primary  yield  nitrolic  acids  and  the  secondary  pseudo-nitrols, 
while  the  tertiary  do  not  react  with  it  at  all.    Thus  from  nitro-ethane, 

CH3— C^^2^^,  *'ethyl-nitrolic  acid,"  CHg.C^^j^^,  an  acid  crystal- 
lizing in  light  yellow  crystals  and  whose  alkaline  salts  are  intensely 
yellow,  is  formed.  Secondary  nitro-propane,  (CH3)2=CH(N02),  gives 
on  the  contrary  "propyl-pseudo-nitrol,"  (CHo)2C=N.O.N02,  or  perhaps 
(CH3)2C=N.O.N02,  a  white  crystalline,  indifferent,  non-acid  substance, 
which  is  blue  either  when  fused  or  when  in  solution.  These  reactions, 
which,  moreover,  only  go  on  in  the  case  of  the  lower  molecular  alcohols, 


KTHUllS  OF  SULPHURIC  ACID. 


103 


(in  the  primary  up  to  Cg,  and  in  the  secondary  up  to  C5),  are  specially 
applicable  for  distinguishing  between  the  primary,  secondary,  or  tertiary 
nature  of  an  alcohol,  (see  p.  78).  The  nitro-hydrocarbons,  which  are 
easilj^  prepared  from  the  iodides,  are  dissolved  in  a  solution  of  potash 
to  which  sodium  nitrite  is  added,  the  solution  acidified  with  sulphuric 
acid  and  again  made  alkaline,  and  then  observed  for  the  production  of 
a  red  colouration,  (primary  alcohol),  a  blue  colouration,  (secondary 
alcohol),  or  no  colouration  at  all,  (tertiary  alcohol). 

Appendix. 

Chloropicrin,  CCI3NO2,  a  heavy  liquid  of  excessively  suf- 
focating smell,  B.  Pt.  112°,  is  formed  from  many  hydrocarbon 
compounds  by  the  simultaneous  action  of  nitric  acid  and 
chlorine,  chloride  of  lime,  etc.  It  is  best  obtained  from  picric 
acid  and  bleaching  powder. 

Di-nitro  derivatives  of  the  saturated  hydrocarbons,  e.g.  Di-nitro-ethane, 
C2H4(N02)2,  whose  potassium  salt  is  an  explosive  yellow  crystalline 
compound  obtained  from  CH3.CHBr(N02) +  KNO2,  also  exist ;  further, 
some  tri-nitro  derivatives,  and  even  tetra-nitro-methane,  C(N02)4  (white 
crystals),  which  last  boils  without  decomposition. 

3.  Derivatives  of  Hypo-nitrous  Acid 

Hypo-nitrous  acid,  HNO  or  H2N2^2>  be  transformed  into  an 
ether  of  the  formula  (02115)2X202,  Diazo-ethoxane,  {Zorn),  an  oil  which 
explodes  even  at  40°.  The  nitroso-compounds  R.NO,  derived  from 
benzene, .  also  belong  to  this  category,  (see  Nitroso-benzene,  OgH5.NO). 
Analogues  in  the  Fatty  Series  are  unknown. 

4.  Ethers  of  the  Chlorine  Acids 

are  known,  e.g.  ethyl  hypochlorite,  O2H5.O.OI,  and  ethyl  perchlorate, 
C2H5.O.OIO3,  both  violently  explosive  liquids. 

5.  Ethers  of  Sulphuric  Acid. 

The  neutral  ethers  are  formed — 
(o.)  From  fuming  sulphuric  acid  and  alcohol ; 
(h)  From  silver  sulphate  and  alkyl  iodide ; 
(c)  From  sulphuryl  chloride  and  alcohol : 

SO2CI2  +  2C2H,OH  =  m.iOG^-R,)^  +  2HCI. 


104      IV.  DERIVATIVES  OF  THE  MONATOMIC  ALCOHOLS. 


The  acid  ethers  or  ether  sulphuric  acids  "  of  the  primary 
alcohols  result  directly  from  their  components.  Secondary 
and  tertiary  alcohols  do  not  yield  them. 

{a)  Ethyl  sulphate,  (02^5)2804,  is  a  colourless  oily  liquid  of 
an  agreeable  peppermint  odour,  insoluble  in  water,  and  solidi- 
fying on  exposure  to  a  strong  cold ;  B.  Pt.  208°.  It  is  quickly 
saponified  (to  ordinary  ether)  upon  warming  with  alcohol, 
also  upon  boiling  with  water,  but  only  slowly  with  cold  water; 
in  the  latter  cases  alcohol  and  sulphuric  acid  are  produced. 

{h)  Ethyl-sulphuric  acid,  C2H,.S04H,  =  C2H5.O.SO3H, 
(Dahit,  1802),  is  obtained  from  a  mixture  of  alcohol  and 
sulphuric  acid,  as  given  under  Ethyl  ether,  method  1,  but  not 
quantitatively,  on  account  of  the  state  of  equilibrium  that 
ensues,  (see  p.  98).  It  is  also  formed  from  ethylene  and 
sulphuric  acid  at  a  somewhat  higher  temperature.  It  differs 
from  sulphuric  acid  by  its  Ba-,  Ca-,  and  Pb-salts  being  soluble, 
and  it  can  therefore  be  easily  separated  from  the  former  by 
means  of  BaCOg,  etc.  It  yields  salts  which  crystallize  beauti- 
fully, but  which  slowly  decompose  into  sulphate  and  alcohol 
on  boiling  their  concentrated  aqueous  solution,  especially  in 
presence  of  excess  of  alkali.  They  are  often  used  instead  of 
ethyl  iodide  in  the  preparation  of  other  ethyl  compounds  by 
double  decomposition. 

The  free  acid  is  prepared  by  adding  the  exact  quantity  of 
sulphuric  acid  required  to  the  barium  salt.  It  is  a  colourless 
oily  liquid  which  does  not  adhere  to  glass,  and  which  slowly 
decomposes  into  alcohol  and  sulphuric  acid,  i.e.  is  saponified, 
on  evaporating  or  preserving  its  solution,  and  quickly  upon 
boiling  it. 

The  methyl-,  amyl-,  etc.  compounds  are  analogous;  the  former  is  also  a 
syrup  which  does  not  adhere  to  glass. 

6.  Derivatives  of  Sulphurous  Acid. 

a.  Ethers  of  Sulphurous  Acid, 

{a)  Ethyl  sulphite,  803(02115)2,  is  an  ethereal  liquid  of  peppermint 
odour,  which  can  be  prepared  from  alcohol  and  SO^Clj  or  SgClg,  and 
which  is  rapidly  saponified  by  water. 


SULPHONIC  ACIDS. 


105 


{h)  Ethyl- sulphurous  acid,  SO3.  HiCoHg).  The  very  unstable  potassium 
salt  of  this  acid  is  obtained  by  the  partial  saponification  of  ethyl  sulphite 
by  potash  solution — 

SOslCoHs)^  +  KOH  =  SOgKlCaHg)  +  C^HgOH. 

The  free  acid  is  incapable  of  existence,  decomposing  immediately  into 
its  components. 

Analogous  ethers  of  other  alcohols  are  known. 

(3,  Sulpho-  or  Sulphonic  Acids  and  their  Ethers. 

(a)  Ethyl-Sulphonic  Acid,  C2H5.SO3H,  {Lowig,  1839  ; 
H,  Kojyp,  1840),  is  a  strong  monobasic  acid,  very  easily  soluble 
in  water  and  hygroscopic,  and  sharply  distinguished  from 
ethyl-sulphurous  acid  by  its  stability,  not  being  saponified  upon 
boiling  its  aqueous  solution  either  with  alkalies  or  acids. 
Boiling  concentrated  nitric  acid  and  free  chlorine  do  not  act 
upon  it,  and  it  requires  fused  potash  to  effect  its  decomposition. 
It  has  a  strongly  acid  and  disagreeable  after-taste.  It  yields 
crystallizable  salts,  e.g.  CgH^.SOgK  +  HgO,  (hygroscopic), 
C.Hg.SOsNa,  (C2H5.S03)2Ba  +  H20,  etc. 

Modes  of  formation.  1.  From  alkyl  iodide  and  sodium 
or  ammonium  sulphite : 

C2H5.I  +  Na2S03  =  C2H5.S03Na  +  Nal. 

2.  By  the  oxidation  of  mercaptans  by  IINO3  : 
C2H5.SH  +  30  =  O2H5.SO3H.' 
The  sulphonic  acids  yield  chlorides  with  PCI5,  e.g.  ethyl- 
sulphonic  acid  gives  ethyl-sulphonic  chloride,  CgH^SOgCl, 
a  liquid  which  boils  without  decomposition  at  177°,  fumes  in 
the  air,  and  is  reconverted  by  water  into  ethyl-sulphonic  and 
hydrochloric  acids.    Nascent  hydrogen  reduces  it  to  mercaptan. 

With  zinc  dust  it  yields  the  zinc  salt  of  a  peculiar,  syrupy,  easily 
soluble  acid,  viz. — 

Ethyl- sulphinic  acid,  C2H5.SO2H,  which  is  likewise  converted  into 
mercaptan  upon  further  reduction.  Its  sodium  salt  yields  ethyl 
sulphone  when  treated  with  ethyl  bromide,  C2HgBr.  It  also  forms  an 
unstable  ether,  isomeric  with  this  latter  compound,  (see  p.  96). 

Methyl-sulphonic  acid,  CH3.SO3H,  was  prepared  by 
Kolbe    in    1845   from    trichloro-methyl-sulphonic  chloride, 


106      IV.  DERIVATIVES  OF  THE  MONATOMIO  ALCOHOLS. 


CCI3.SO2CI,  (produced  from  CS2,  CI,  and  H2O).  It  is  a  syrupy 
liquirl. 

Ethyl-sulphonic  ethyl  ether,  C2H5.S03.C2H^,  is  isomeric 
with  ethyl  sulphite,  and,  being  an  ether  of  the  more  stable 
ethyl-sulphonic  acid,  is  only  partially  saponifiable.  It  is  pre- 
pared from  silver  sulphite  and  ethyl  iodide.  B.  Pt.  213°. 
The  sulphonic  ethers  have  considerably  higher  boiling  points 
than  the  isomeric  sulphurous  ethers. 

Constitution.  From  the  formation  of  the  sulphonic  acids 
from  mercaptans  by  oxidation,  and  the  (indirect)  reversibility 
of  this  reaction,  it  follows  that  the  sulphur  in  them  is  directly 
bound  to  the  alcohol  radicle ;  if,  then,  sulphur  is  regarded  as 
hexavalent,  ethyl  sulphonic  acid  has  the  constitution 

From  this  we  arrive  at  the  constitution  of  sodium  sulphite  as  being 
Na — (SOgNa),  of  the  hypothetical  sulphurous  acid  as  H — (SO3H),  and 
of  sulphuric  acid  as  H — 0 — (SO3H). 

The  real  easily  saponifiable  sulphurous  ethers  therefore 
manifestly  contain  the  sulphur  not  bound  directly  to  the 
carbon  but  through  oxygen,  so  that  for  them  the  following 
formulae  hold:  ethyl-sulphurous  acid,  C2H^.O.S02H,  and 
ethyl- sulphurous      acid      ether,      C2H5O.SO.O.C2H5,  or 

Related  to  methyl-sulphonic  acid  are  ;  Methane-di-sulphonic  acid, 
CH2(S03H)2,  a  crystalline  body,  Methane-tri-sulphonic  acid, 
CH(S03H)3,  also  crystalline,  Ethylene-  and  Ethidene-di- sulphonic  acids, 
C2H4(S03H)2,  Propane-tri-sulphonic  acid,  03115(80311)3,  etc. ;  these  may 
also  be  regarded  as  sulphurous  acid  derivatives  of  polyatomic  alcohols. 

7.  Ethers  of  Tri-  and  Polybasic  Acids. 

Ethers  of  phosphoric  acid :  P0(0E)3,  P0(0R)2(0H),  and 
P0(0E,)(0H)2,  (E/  =  alkyl),  exist,  as  do  also  similar  compounds 
of  phosphorous  and  hypophosphorous  acids.  The  phosphinic 
acids,  etc.,  are  related  to  the  two  last-mentioned  classes.  (See 
phosphines.) 

Ethers  of  boracic  and  silicic  acids  are  also  known. 


njtrilb:s  and  iso-nttiules. 


107 


8.  Alcoholic  Derivatives  of  Hydrocyanic  Acid. 

(Nitriles  and  Iso-nitriles.) 

Hydrocyanic  acid,  HON,  yields  two  classes  of  derivatives 
by  the  exchange  of  its  hydrogen  atom  for  alcohol  radicles, 
neither  of  which  can  be  grouped  among  the  ethers,  since 
they  do  not  go  back  into  alcohol  and  hydrocyanic  acid  on 
saponification,  but  decompose  in  another  direction. 

a.  Cyanides  of  the  Alcohol  Eadicles  (Nitriles). 

These  are  either  colourless  liquids,  volatile  without  decom- 
position, or  solids,  of  a  not  unpleasant  ethereal  odour  slightly 
resembling  that  of  leeks,  lighter  than  water,  and  relatively 
stable.  The  lower  members  are  miscible  with  water,  but  the 
higher  ones  insoluble  in  it.  They  boil  at  about  the  same 
temperatures  as  the  corresponding  alcohols. 

Formation.  1.  By  heating  alkyl  iodide  with  potassium 
cyanide,  or  potassium  ethyl-sulphate  with  potassium  ferro- 
cyanide : 

CH3I  +  KCN  =  KI  +  CH3.CN 

Methyl  cyanide. 

2.  By  distillation  of  the  ammonium  salts  of  monobasic  acids 
which  contain  one  atom  of  carbon  more  than  the  alcohol 
which  would  be  used  in  method  1,  and  treatment  of  the 
amides  which  are  at  first  produced  with  separation  of  water, 
with  a  dehydrating  agent  such  as  P2O5,  (Hofmann),  PCI5  or 
P2Sr,,  (see  imide  chlorides  and  thiamides) ;  also  by  treating  the 
ammonium  salts  of  the  acids  directly  with  PgO^  : 

a.    CH3.COOH  +  NH3  =  H2O  +  CH3.CO.NH2 

Acetamide. 

6.    CH3.CO.NH2  -  H2O  =  CH3.CN. 

As  a  consequence  of  this  mode  of  formation  these  com- 
pounds are  also  termed  nitriles  of  the  monobasic  acids,  e.g, 
CH3.CN,  methyl  cyanide  or  Aceto-Nitrile ;  CgHg.CN,  propio- 
nitrile,  etc. 

3.  The  higher  nitriles,  in  which  C>5,  result  from  the 
amides  of  acids  of  the  acetic  series  containing  one  atom  of 


108      IV.  DERIVATIVES  OF  THE  MONATOMIC  ALCOHOLS. 


carbon  more  in  the  molecule,  and  also  from  the  primary 
amines  with  the  same  numl)er  of  carbon  atoms,  upon  treat- 
ment with  bromine  and  caustic  soda  solution,  (Hofmann). 
See  amides. 

Behaviour.  1.  These  compounds  are  very  active  chemically. 
When  heated  with  acids  or  alkalies  or  superheated  with  water, 
they  break  up  into  the  acids  from  which  they  were  originally 
prepared  and  ammonia ;  amides  may  be  formed  here  as  inter- 
mediate products : 

CH3.CN  +  2H,0  =  CH3.COOH  +  NH3. 

This  is  a  reaction  of  great  moment,  because  it  leads  from 
the  alcohols  C,,Hon+i.OH  to  the  acids  of  the  acetic  series, 
CnHsn+i.COOH,  richer  than  those  alcohols  by  one  atom  of 
carbon.  (Bumas,  Malaguti,  Le  Blanc,  and  also  Franhland  and 
Kolhe,  1847.) 

2.  Just  as  acetamide  is  formed  by  the  taking  up  of  water,  so  is  thio- 
acetamide  by  the  taking  up  of  sulphuretted  hydrogen. 

3.  By  the  addition  of  halogen  hydride,  amido-chlorides  or  imido- 
chlorides  result ;  by  the  addition  of  ammonia  bases,  amidines. 
Halogens  also  form  easily  decomposable  addition-products,  (see  acid 
derivatives). 

4.  Combination  with  hydrogen  leads  to  amines,  (p.  113): 

CH3.CN  -f  2H2  -  CH3.CH2.NH2. 

Ethylamine. 

5.  Metallic  potassium  or  sodium  frequently  induces  polymerization  ; 
thus  methyl  cyanide  yields  in  this  way  cyanmethine,  a  mono-acid  base 
crystallizing  in  prisms. 

For  Constitution,  see  Iso-nitriles. 

Aceto-nitrile,  CH3.CN,  is  present  in  the  products  of  distil- 
lation from  the  vinasse  of  sugar  beet  and  in  coal  tar.  B.  Pt. 
82° ;  combustible,  and  miscible  with  water. 

Propio-nitrile,  CgHg.CN,  Butyro-nitrile,  C3H7.CN,  and  Valero- 
nitrile,  C4H9.CN,  are  liquids  of  agreeable  bitter  almond  oil  odour; 
Palmito-nitrile,  C15H31.CN,  is  like  paraffin. 

Cyanogen  compounds  of  unsaturated  alcohol  radicles  also  exist,  e.g. 
AUyl  Cyanide,  C3H5.CN,  (see  crotonic  acid). 

Fulminate  of  Mercury,  probably  CHg(N02).CN,  is  to  be 
regarded  as  a  salt  of  the  non-existent  Nitro-aceto-nitrile, 
CH2(N02).CN,  whose  H-atom  has  been  rendered  easily  re- 


ISO-NITRILES. 


109 


placeable  by  metals  through  the  acidifying  influence  of  the 
NO.j-  and  GN-groups.  It  is  obtained  by  warming  alcohol 
with  nitric  acid  and  mercuric  nitrate,  and  forms  silky  glancing 
prisms  which  explode  with  the  utmost  violence  upon  being 
heated  or  struck.  The  analogous  fulminate  of  silver  is  even 
more  explosive.  Concentrated  HCl  decomposes  them  into 
CO2  and  HCl-hydroxylamine. 

p.  Iso-cyanides  (Iso-nitriles  or  Carbamines). 

Colourless  liquids  easily  soluble  in  alcohol  and  ether,  but 
only  slightly  soluble  or  insoluble  in  water,  of  weak  alkaline 
reaction,  unbearable  odour,  and  poisonous  properties,  and 
boiling  somewhat  lower  than  the  nitriles. 

Formation.  1.  By  heating  the  iodides  of  the  alcohol 
radicles  with  silver  cyanide  instead  of  potassium  cyanide, 
(Gautier),  a  double  compound  with  cyanide  of  silver  being  first 
formed : 

CNAg  +  C2H5l  =  Agl  +  C^H^NC. 

Ethyl  iso-cyanide. 

2.  In  small  quantity,  along  with  the  nitriles,  when  potassium  alkyl- 
sulphate  is  distilled  with  potassium  cyanide. 

3.  By  the  action  of  chloroform  and  alcoholic  potash  upon 
primary  amines,  (Hofmann,  1869) : 

CH3.NH2  +  CHCI3  +  3K0H  =  CH3.NC  +  3KC1  +  3H2O. 

Behaviour,  1.  The  iso-nitriles  differ  fundamentally  from  the 
nitriles  by  their  behaviour  with  water  or  dilute  acids.  When 
strongly  heated  with  water,  or  with  acids  in  the  cold,  they 
split  up  into  formic  acid  and  amine  bases  containing  one  atom 
of  carbon  less  than  themselves,  from  which  latter  compounds 
they  can  be  prepared : 

CH3.NC  +  2H2O  =  CH3.NH2  +  HCO2H. 
Unlike  the  nitriles,  they  are  very  stable  towards  alkalies. 

2.  The  iso-nitriles  are  also  capable  of  forming  addition  products  with 
hydrochloric  and  hydrosulphuric  acids,  etc.,  compounds  different  from 
those  given  by  the  nitriles  ;  thus,  with  HCl  they  yield  crystalline  salts 
which  are  violently  decomposed  by  water  into  amine  and  formic  acid. 

3.  Some  of  the  iso-nitriles  change  into  the  isomeric  nitriles 
on  being  heated. 


110     IV.  DERIVATIVES  OF  THE  MON ATOMIC  ALCOHOLS. 


Methyl  iso-cyanide,  CH3.NC.    B.  Pt.  58°. 
Ethyl  iso-cyanide,  CgHg.NC.    B,  Pt.  82°. 

Constitution  of  the  Nitrites  and  Iso-nitriles.  The  constitu- 
tion of  the  nitriles  follows  from  their  close  relation  to  the  acids. 
The  carbon  atom  of  the  cyanogen  group  — CN  remains 
attached  to  the  alcohol  radicle  after  the  action  of  saponifying 
agents,  and  is  therefore  directly  bound  to  the  carbon  atom  of 
the  latter.  The  nitrogen  on  the  other  hand  is  split  off,  and  is 
thus  not  directly  bound  to  the  alcohol  radicle.  Consequently 
aceto-nitrile  has  the  constitution  :  CH3  — C=N. 

In  the  case  of  the  iso-nitriles,  however,  it  is  the  nitrogen 
which  must  be  directly  bound  to  the  alcohol  radicle,  as  their 
close  connection  with  the  amine  bases  shows,  the  amines  being 
easily  prepared  from  and  reconverted  into  the  iso-nitriles. 
The  carbon  atom  of  the  cyanogen  group,  on  the  contrary,  is 
split  off  on  decomposition  by  acid,  and  is  consequently  not 
bound  directly  to  the  alcohol  radicle  but  only  through  the 
nitrogen.  The  constitutional  formula  of  the  iso-nitriles  there- 
fore is  R — NC,  probably  E — N=C,  e,g.  methyl  carbamine, 
CH3— N=C,  etc. 

The  difference  between  the  two  kinds  of  compounds  is  sufficiently 
emphasized  as  a  rule  by  writing  them  CHg.CN  and  CHg.NC. 

D.  Nitrogen  Bases  of  the  Alcohol  Radicles. 

By  the  introduction  of  alcohol  radicles  in  place  of  hydrogen 
into  ammonia  or  its  salts,  the  important  class  of  ammonia 
bases  or  amines  and  ammonium  bases  of  the  alcohol  radicles 
is  produced. 

The  amines  containing  the  lower  alcohol  radicles  bear  the 
closest  resemblance  to  ammonia,  being  even  more  strongly 
basic  than  the  latter.  They  have  an  ammoniacal  odour,  give 
rise  to  white  clouds  with  volatile  acids,  combine  with  hydro- 
chloric acid,  etc.  to  salts  with  evolution  of  heat,  and  yield 
double  salts  with  platinic  and  gold  chlorides.  They  further 
precipitate  many  metallic  salts,  the  precipitates  being  fre- 
quently soluble  in  excess. 

The  lowest  members  of  this  class  are  combustible  gases 


NITROGEN  BASES. 


Ill 


readily  soluble  in  water.  The  next  are  liquids  of  low  boiling 
point,  also  at  first  easily  soluble,  but  the  solubility  in  water 
diminishes  with  increasing  carbon  (more  quickly  in  the 
nitrile-  than  in  the  amido-bases),  and  also  the  volatility, 
until  the  highest  members  of  the  series,  such  as  tricetyhimine, 
(Cj(3H33)3N,  are  at  the  ordinary  temperature  solid  odourless 
substances  of  high  boiling  point,  insoluble  in  water  but  soluble 
in  alcohol  and  ether,  readily  combining  however  with  acids 
to  salts,  like  the  others. 

All  amine  bases  are  considerably  lighter  than  water. 

The  ammonium  bases  are  solid  and  very  hygroscopic,  and 
exceedingly  like  potash  in  properties. 

Classification,  The  nitrogen  bases  of  the  alcohol  radicles 
are  divided  into  primary,  secondary,  tertiary,  and  quaternary 
bases,  according  as  they  contain  one,  two,  three,  or  four 
alcohol  radicles ;  the  three  first  are  derived  from  ammonia, 
and  the  last  from  the  hypothetical  ammonium  hydroxide, 
NH,.OH. 


Amines  or  Ammonia  Bases. 

Ammonium  Bases. 

Primary  or 
Amido-bases. 

Secondary  or 
Imido-bases. 

Tertiary  or 
Nitrile-bases. 

Quaternary 
Bases. 

NH,(CH3) 
Methylamine 
(Gas.) 

Ethylamine 
(B.  Pt.  19°). 

etc. 

Di-methylamine 
(B.  Pt.  8°). 

NHlC^Hg), 
Di-ethylamine 
(B.  Pt.  57°). 

etc. 

.  N(CH3)3 
Tri-methylamine 
(B.  Pt.  9°). 

N(C2H,)3 
Tri-ethylamine 
(B.  Pt.  89°). 

etc. 

N(CE3)J 
Tetra-methyl- 
ammonium  iodide. 

N(C2H5)40H 
Tetr-ethyl-am- 
moniu  m  -hydroxide. 

etc. 

Occurrence,  Some  individuals  of  this  series  occur  in  nature, 
e.g.  methylamine  and  tri-methylamine. 

Modes  of  formation.  1.  Methylamine,  ethylamine,  etc.,  are 
obtained  by  treating  methyl  or  ethyl  etc.  cyanate  with  potash 
solution,  {Wurtz,  1848): 

CO.NlC^H,)  +  2K0H  =  C2H5.NH2  +  K^COg. 
This  method  of  formation  yields  only  primary  bases. 


112      IV.  DERIVATIVES  OF  THE  MONATOMIC  ALCOHOLS. 


l\  The  iso-thiocyanic  ethers  or  mustard  oils  (see  these) 
also  yield  those  bases  upon  heating  with  concentrated  acids. 

2.  By  the  direct  introduction  of  the  alcohol  radicle  into 
ammonia  by  heating  a  concentrated  solution  of  the  latter  with 
methyl  iodide,  chloride^  or  also  nitrate,  ethyl  iodide,  etc.  In 
this  reaction  an  atom  of  hydrogen  is  first  exchanged  for  an 
alcoholic  radicle,  and  then  the  base  produced  combines  with 
the  halogen  hydride,  formed  at  the  same  time,  to  a  salt, 
thus  : 

(1.)         NH^H  +  CH3I  =  NH2.CH3,  HI. 
From  the  methylamine  hydriodide  thus  produced,  free 
methylamine  can  easily  be  got  by  distilling  with  potash : 
NH,(CH3),  HI  +  KOH  =  NH2(CH3)  +  KI  +  H^O. 
The  methylamine  can  now  combine  further  with  methyl 
iodide  to  hydriodide  of  di-methylamine  : 

(II.)       NH2(CH3)  +  CH3l  =  NH(CH3)2HI, 
which,  in  its  turn,  yields  the  free  base  with  potash.  This 
latter  can  again  combine  with  methyl  iodide  : 

(III.)      NH(CH3)2  +  CH3l  =  N(CH3)3HI, 
the  salt  so  produced  yielding  tri-methylamine  as  before. 
Finally  the  tri-methylamine  can  once  more  take  up  methyl 
iodide : 

(IV.)         N(CH3)3  +  CH3l  =  N(CH3y. 

The  compound  obtained,  tetra-methyl-ammonium  iodide,  is 
however  no  longer  a  salt  of  an  amine  base  but  of  an 
ammonium  one,  and  is  not  decomposed  on  distillation  with 
potash  solution. 

By  using  various  dissimilar  alkyl  iodides  instead  of  methyl  iodide 
alone,  bases  are  got  containing  different  alcohol  radicles  together, 
i.e.,  "mixed"  amines,  etc.,  e.g.,  methyl-propylamine,  NH(CH3)(C3H7)j 
methyl-ethyl-propylamine,  N(CH3)(C2H5)(C3H7). 

The  reactions  I.  to  IV.,  given  above,  do  not  in  reality  follow  each 
other  in  perfect  order  but  go  on  simultaneously,  the  bases  being  partly 
liberated  from  the  hydriodates  by  the  ammonia,  and  so  being  free  to 
react  with  new  halogen  alkyl.  The  product  obtained  by  distillation 
with  potash  is  therefore  a  mixture  of  all  the  three  amine  bases. 

These  cannot  be  separated  by  fractional  distillation,  and  so  their 
different  behaviour  with  oxalic  ether,  0202(002115)2,  is  made  use  of  for 
the  purpose.    Methylamine  reacts  with  this  ether  to  form  chiefly  (1) 


NITROGEN  BASES  ;  FORMATION  OF. 


113 


di-metliyl-oxamide,  C20o(NH. 0113)2,  (solid),  and  (2)  some  methyl- 
oxamic  ether,  C202(OC2H5)(NH.CH3),  (liquid);  di-methylaiiiine  yields 
(3)  the  ethyl  ether  of  di-methyl  oxamic  acid,  C202(GC2H5)N(CH3)2, 
(liquid),  while  tri-methylamine  does  not  react  with  oxalic  ether.  Upon 
warming  the  product  of  the  reaction  on  the  waterbath,  the  latter 
base  distils  over,  and  the  remaining  compounds  can  then  be  separated 
by  special  methods,  (for  which  see  B.  3,  776  ;  8,  760),  and  individually 
decomposed  by  potash,  (1)  and  (2)  yielding  methylamine,  and  (3)  di- 
methylamine. 

3.  The  nitro-compounds  yield  primary  amido-compounds  on 
reduction  (see  p.  100),  thus  : 

CH3.NO2  +  3H2  =  CH3.NH2  4-  2Bfi. 

4.  The  nitriles,  including  hydrocyanic  acid,  are  capable  of 
taking  up  four  atoms  of  hydrogen  (see  p.  108),  and  forming 
primary  amines,  (Mendius,  1862): 

CH3.CN  +  2H2  =  CH3.CH2.NH2  =  C2H,.NH2. 

Ethylamine. 

H.CN  +  2H2  =  CH3.NH2. 

Methylamine. 

4*.  The  iso-nitriles  are  decomposed  by  hydrochloric  acid,  with  forma- 
tion of  the  primary  amine  bases  from  which  they  are  also  obtained 
(p.  109). 

5.  Primary  amines,  in  which  0>6,  are  prepared  according 
to  Hofmann's  method,  by  the  action  of  bromine  and  caustic 
soda  solution  upon  the  amides  of  acids  containing  one  carbon 
atom  more  than  themselves  (see  amides). 

6.  Primary  amines  likewise  result  from  the  reduction  of  the  oximes 
or  hydrazones,  (see  pp.  134,  142,  and  373). 

Isomers.  Numerous  isomers  exist  among  the  amine  bases, 
as  the  following  table  shows  : 


C2H7N. 

(J4H„N. 

Isomers 

NH(CH3), 

NH,(C3H,) 
NH(CH3)(C,H5) 
N(CH3)3 

NH,(C4H,,) 
NH(CH3)(C,Hj)  and  NH(C2H5)j 

This  kind  of  isomerism  is  the  same  as  that  of  the  ethers  (p.  93),  i.e., 
metamerism.  From  (O3H7)  onwards,  isomerism  can  also  occur  in  the 
alcohol  radicles.  According  to  theory,  as  many  amines  On  as  alcohols 
Cn-i-i  are  capable  of  existence. 

(506)  H 


114     IV.  DERIVATIVES  OF  THE  MONATOMIO  ALCOHOLS. 


Behaviour,  1.  For  general  behaviour,  see  above.  When 
combined  with  acids  to  salts,  the  amines  behave  exactly  like 
ammonia,  and  the  ammonium  bases  like  potash  : 

CH3.NH2  +  HCl  -  CH3.NH2,  HCl  -  (CH3)NH3C1. 
[N(CH3)J0H  4-  HCl  =  [N(CH3)JC1  +  H^O. 
The  salts  so  obtained  are  white,  crystalline,  frequently 
hygroscopic  compounds,  easily  soluble  in  water.  The  chlorides 
form,  with  platinic  chloride,  crystalline  double  compounds 
whose  composition  is  analogous  to  that  of  ammonio-platinic 
chloride,  2NH4CI,  PtCl^ ;  e.g.,  hydrochlorate  of  methylamine- 
platinic  chloride,  2(NH2[CH3]HC1),  PtCl^. 

The  same  applies  to  the  gold  double  salts,  e.g., 
NH2(C2H5)HC1,  AUCI3. 

2.  Saponifying  agents  such  as  alkalies  and  acids  do  not 
affect  the  nitrogen  bases  of  the  alcohol  radicles,  and  oxidizing 
agents  only  with  difficulty.    (See  B.  8,  1237.) 

3.  The  different  classes  of  amine  bases  are  distinguished 
from  each  other  by  the  primary  having  two  hydrogen  atoms, 
the  secondary  one,  but  the  tertiary  none  replaceable  by  alcohol 
radicles ;  the  same  applies  to  substitution  by  acid  radicles. 
The  products  thus  resulting  from  isomeric  amines  are  dis- 
tinguished from  one  another  by  analysis.  Thus  propylamine 
gives  with  methyl  iodide  the  base  C3H^N(CH3)2,  =  C^H^^N  • 
the  isomeric  methyl-ethylamJne  the  base  (CH3)(C2H5)N(CH3), 
=  C4H9N;  while  tri-methylamine,  (CH3)3N,  =  C3H9N,  likewise 
isomeric,  remains  unaltered. 

The  primary  bases  further  differ  from  the  others  in  their 
behaviour  with  chloroform,  carbon  bisulphide  and  nitrous  acid. 

4.  Only  the  primary  bases  react  with  chloroform  and  alco- 
holic potash,  with  formation  of  iso-nitriles  (p.  109). 

5.  VS^hen  warmed  with  carbon  bisulphide  in  alcoholic  solution,  the 
primary  and  secondary-,  but  not  the  tertiary  bases,  react  to  form 
derivatives  of  thio-carbamic  acids.  (See  carbonic  acid  derivatives.) 
Should  the  amines  be  primary  ones,  the  characteristically  smelling  iso- 
thio-cyanates  are  produced  upon  heating  the  thio-carbamic  derivatives 
with  a  solution  of  HgClg,      Senfol"  reaction). 

6.  Nitrous  acids  act  upon  the  primary  bases  to  reproduce 
the  alcohols,  e.g,: 


NITROGEN  BASES  ;  BEHAVIOUR  OF. 


115 


CH3.NH2  +  H.O.NO  =  CH3.OH  +  N2  +  H2O. 

Secondary  bases,  on  the  other  hand,  yield  with  nitrous  acid 
nitroso-compounds,  e.g.  "  dimethyl-nitrosamine"  : 

(CH3)2NH  +  NO.OH  =  (CH3)2N.NO  +  H2O. 

These  nitroso-compounds  are  yellow-coloured  liquids  of 
aromatic  odour,  which  boil  without  decomposition.  (Geuther.) 
They  regenerate  the  secondary  bases  upon  treatment  with 
strong  reducing  agents,  and  also  upon  warming  with  alcohol 
and  hydrochloric  acid.  Weak  reducing  agents  however  con- 
vert them  into  hydrazines  (p.  118). 

The  nitrosamines  are  frequently  of  great  service  in  the  purification  of 
the  secondary  bases. 

Nitrous  acid  has  no  action  upon  tertiary  amines. 

7.  While  the  amine  bases  are  liberated  from  their  salts  by 
alkalies,  the  free  bases  of  the  quaternary  salts,  e.g.  tetra- 
methyl-ammonium  iodide,  cannot  be  prepared  from  these  by 
treatment  with  potash,  because  they  are  as  strongly  basic  as 
the  latter,  if  not  even  more  so.  The  salts  however  behave 
like  hydriodates,  for  instance  towards  AgNOg,  and  their  bases, 
e.g.  N(CH3)40H,  can  be  separated  by  acting  upon  them  with 
moist  silver  oxide.  They  are  extraordinarily  like  caustic 
potash.  They  cannot  be  distilled  without  decomposition,  but 
break  up  on  distillation  with  reproduction  of  the  tertiary  base, 
the  tetra-methyl  base  yielding  in  addition  methyl  alcohol,  and 
the  homologous  bases  olefine  and  water,  thus : 

N(CH3)4.0H  =  N(CH3)3  +CH3.OH. 

They  are  of  great  interest  for  the  question  of  the  valency  of  nitrogen, 
since  they  are  more  difficult  to  explain  on  the  assumption  of  its  being 
trivalent  than  pentavalent.  (Cf.  trimethyl-sulphine  hydroxide.)  The 
fact  that  the  salts  N(CH3)2(C2H5)  +  C.HgCl,  and  N(CH.3)(aH5),  +  CH3CI 
are  identical,  speaks  in  favour  of  the  nitrogen  in  them  being  pentavalent. 
[Meyer  and  Lecco. ) 

8.  The  quaternary  iodides  go  back  into  tertiary  base  and 
alkyl  iodide  ii})on  heating.  They  combine  with  two  or  four 
atoms  of  bromine  or  iodine  to  tri-  and  penta-bromides  or 
-iodides,  e.g.  l^{C}i.^\l\  (dark  needles),  and  N(C2H5)4Ll2 


116      IV.  DERIVATIVES  OF  THE  MONATOMIC  ALCOHOLS. 

(aziire-blue  needles).  These  latter  must  be  looked  upon  as 
addition-compounds_,  since  they  readily  lose  their  additional 
halogen  again. 

Hepta-  and  Ennea-iodides  also  exist. 


Methylamine,  CH3NH2.  Occurs  in  Mercurialis  perennis 
and  annua  mercurialin  in  the  distillate  from  bones  and 
wood,  and  in  herring  brine.  It  is  produced  in  many  decom- 
positions of  organic  compounds,  e.g.  from  alkaloids,  as  when 
caffeine  is  boiled  with  hydrate  of  baryta;  also  by  heating 
hydrochlorate  of  tri-methylamine  to  285°. 

It  is  most  easily  prepared  from  acetamide,  caustic  soda,  and 
bromine.  (B.  18,  2737.)  It  is  more  strongly  basic  and  even 
more  soluble  in  water  than  ammonia,  has  a  powerful  am- 
moniacal  and  at  the  same  time  fish-like  odour,  and  burns  with 
a  yellowish  flame.  Its  aqueous  solution,  like  that  of  ammonia, 
precipitates  many  metallic  salts,  frequently  redissolving  the 
precipitated  hydroxides ;  it  also  redissolves  silver  chloride. 

Unlike  ammonia,  it  does  not  dissolve  Ni(0H)2  and  Co(OH)2. 

The  hydrochlorate,  NH2(CH3),  HCl,  forms  large  glittermg  plates,  and 
is  very  hygroscopic  and  easily  soluble  in  alcohol,  the  platinum  salt 
crystallizes  in  golden  scales  or  hexagonal  tables,  the  sulphate  forms 
an  alum  with  Al2(S04)3  -f-  24H2O,  and  a  carbonate  also  exists. 

Di-methylamine,  (CB[3)2NH.  Occurs  in  Peruvian  guano 
and  pyroligneous  acid,  and  is  formed  e.g.  by  decomposing 
nitroso-dimethyl-aniline  by  caustic  soda  solution. 

Tri-methylamine,  (CH3)3N.  Is  pretty  widely  distributed  in 
nature,  being  found  in  considerable  quantity  in  Chenopodium 
vulvaria,  also  in  Arnica  montana,  in  the  blossom  of  Crataegus 
oxyacantha  and  of  pear,  and  in  herring  brine.  {JVertheim.) 

It  is  obtained  as  a  decomposition  product  from  complicated 
organic  compounds  containing  nitrogen,  e.g.  from  the  betaine 
of  beetroot,  and  therefore  along  with  ammonia,  di-methylamine, 
etc.,  methyl  alcohol  and  aceto-nitrile  by  the  distillation  of 
vinasse.  It  possesses  an  ammoniacal  and  pungent  fish-like 
odour.  Is  used  as  bicarbonate  in  the  preparation  of  potash, 
and  combines  with  carbon  bisulphide. 


HYDRAZINES. 


117 


Tetra-methyl-ammonium  iodide,  N(CH3)4l,  is  obtained  in 
large  quantity  directly  from  NH3  +  CH3I.  It  crystallizes  in 
white  needles  or  large  prisms,  and  has  a  bitter  taste. 

Tetra-methyl-ammonium  hydroxide,  N(CH3)40H.  Fine 
hygroscopic  needles.  It  forms  a  number  of  salts,  among  others 
a  platinum  double  salt,  sulphide,  polysulphide,  -cyanide,  etc.; 
many  of  these  are  poisonous. 

Ethylamine,  C2II5NH2.  For  its  preparation  by  Hofmann's 
method,  the  crude  ethyl  chloride  which  is  obtained  as  a  bye- 
product  in  the  manufacture  of  chloral  may  be  used.  It  has  a 
strongly  ammoniacal  smell  and  biting  taste,  mixes  with  water 
in  every  proportion  with  evolution  of  heat,  and  burns  with  a 
yellow  flame.  It  dissolves  Al2(0II)g  but  not  Fe2(0H)g,  also 
Cu(0H)2  with  difficulty,  but  not  Cd(0H)2. 

Ethyl-nitrogen  chloride,  C2H5.NCI2,  is  a  yellow  oil  of  a  most  un- 
pleasant piercing  odour,  obtained  from  the  above  compound  with 
chloride  of  lime. 

Di-ethylamine,  (C2H5)2NH,  does  not  dissolve  Zn(0II)2. 

Triethylamine,  (C2H5)3N,  is  an  oily  strongly  alkaline  liquid, 
only  slightly  soluble  in  water.  The  precipitates  which  it  gives 
with  solutions  of  metallic  salts  are  mostly  insoluble  in  excess 
of  the  precipitant. 

Vinylamine,  (CgHgjNHg.    Easily  decomposable. 

Appendix:  Hydrazines. 

As  hydrazines  are  designated  by  E.  Fischer  (A.  190,  67 ; 
199,  281,  294)  a  series  of  peculiar  bases,  mostly  liquid  and 
closely  resembling  the  amines,  but  containing  two  atoms  of 
nitrogen  in  the  molecule,  and  diff'ering  from  the  latter  especially 
by  their  capability  of  reducing  an  alkaline  solution  of  cupric 
oxide,  (Fehling^s  solution),  for  the  most  part  even  in  the  cold. 
They  are  derived  from  "  Diamide  or  "  Hydrazine," 
NH2 — NH2,  a  compound  of  which  but  little  is  yet  known. 
(Ctirtius,  B.  20,  1633).  We  distinguish  between  primary 
hydrazines,  R — NH — NHg,  and  secondary,  E2=N — NHg, 
according  as  one  or  both  of  the  hydrogen  atoms  which  are 


118     IV.  DERIVATIVES  OF  THE  MON ATOMIC  ALCOHOLS. 


attached  to  an  atom  of  nitrogen  are  replaced  by  alcohol 
radicles  (R). 

Ethyl-hydrazine,  C2H^— NH— NHg.  When  di-ethyl  urea 
is  treated  with  nitrous  acid,  a  nitroso-compound  is  formed, 
which  is  changed  by  reduction  with  zinc  dust  and  acetic  acid 
into  the  so-called  "  di-ethyl-semi-carbazide."  This  last  decom- 
poses upon  being  heated  with  hydrochloric  acid  into  carbonic 
acid,  ethylamine,  and  ethyl-hydrazine  : 

CO<nh_c;h',  ^Q<N(NO)-cX  ^|^<N(NH,)-G,H, 

Di-ethyl  urea.         Nitroso  compound.  Di-ethyl-semi- 

carbazide. 

CO(NHC2H5)(N[NH2]C2H5)fH20  =  C02  +  NH2C2H5  +  NH(NH2).C2H5. 

Ethyl-hydrazine  is  a  colourless  mobile  liquid  of  ethereal  and 
faintly  ammoniacal  odour,  boiling  at  100°.  It  is  very  hygro- 
scopic, forms  white  clouds  with  moist  air,  dissolves  in  water 
and  alcohol  with  evolution  of  heat,  and  corrodes  cork  and 
caoutchouc, 

K2S2O7  acts  upon  it  to  form  potassium  ethyl-hydrazine  sulphite, 
C3H5NH — NH — SO3K,  which  in  its  turn  reacts  with  mercuric  oxide  to 
yield  potassium  diazo-ethane-sulphonate,  C2H5N=N — SO3K,  a  diazo- 
compound  which  detonates  violently  upon  warming.  (See  diazo- 
benzene.) 

Di-ethyl-hydrazine,  (02115)2^ — NH2,  is  prepared  from  di- 
ethylamine  by  transforming  it  into  di-ethyl-nitros amine  by  the 
nitrous  acid  reaction,  and  then  reducing  the  latter : 

(C2H5)2N-NO  +  2R,  =  (C2H5)2N-NH2  +  H,0. 

It  resembles  ethyl-hydrazine  closely. 

Tetra- ethyl- tetrazone,  (02115)2 — N — N=N— N — (02115)2,  a  colourless 
strongly  basic  oil,  volatile  with  steam,  results  upon  treating  di-ethyl- 
hydrazine  with  mercuric  oxide. 

For  the  behaviour  of  hydrazines  with  aldehydes  and  ketones, 
see  these. 

The  constitution  of  the  hydrazines  follows  from  their  modes 
of  formation.  Since  in  di-ethyl-nitrosamine,  (C2H^)2N — NO, 
for  instance,  the  nitroso-group  NO  must  be  bound  to  the 
nitrogen  of  the  amine  and  not  to  the  carbon,  judging  from  the 


MOSPHORUS  COMPOUNDS. 


119 


ease  with  wliieh  it  can  be  separated,  (p.  115),  so  the  same 
h'nking  of  tlie  atoms  must  be  assumed  in  the  hydrazines,  which 
are  formed  from  the  nitroso-compounds  by  reduction,  i.e.  by 
exchange  of  0  for  Hg.  In  agreement  with  this  stands  the  easy 
re-oxidation  of  the  hydrazines  to  di-ethylamine  by  an  alkaline 
solution  of  cupric  oxide.  The  hydrazines  are  very  stable  as 
regards  reducing  agents. 

When  one  H-atom  in  each  of  the  two  amido-groups  is  replaced, 
however,  hydrazo-compounds,  R — NH — NH — R,  are  formed.  (See 
Aromatic  hydrazo-compounds.) 

E.  Phosphorus-,  Arsenic-,  etc.,  Compounds. 

1.  Phosphorus  compounds  of  the  alcohol  radicles. 

Just  as  amines  are  derived  from  ammonia,  so  from  phos- 
phuretted  hydrogen,  PH3,  are  derived  primary,  secondary,  and 
tertiary  phosphines  by  the  exchange  of  hydrogen  for  alcoholic 
radicles,  and  to  these  must  likewise  be  added  quaternary  com- 
pounds, the  phosphonium  bases.  These  correspond  closely  with 
the  amines  in  composition  and  in  some  of  their  properties,  e.g, 
they  are  not  saponifiable.  But  they  differ  from  them  in  the 
following  points  : 

(1)  Phosphuretted  hydrogen  possessing  hardly  any  basic 
character,  they  are  only  weak  bases.  Ethyl  phosphine  does 
not  affect  litmus  and  its  salts  decompose  with  water.  The 
salts  of  the  secondary  and  tertiary  compounds,  however,  do 
not  thus  decompose,  this  showing  that  the  alcohol  radicles 
exercise  a  slightly  basic  action. 

2.  They  also  resemble  phosphuretted  hydrogen  in  being 
readily  inflammable,  and  they  are  consequently  rapidly 
oxidized  in  the  air  and  easily  take  fire  of  themselves. 

3.  They  are  oxidized  by  careful  addition  of  oxygen  to  acids 
or  oxides  derived  from  phosphoric  acid,  and  they  also  combine 
in  part  with  sulphur  or  halogen. 

4.  Corresponding  with  the  disagreeable  smell  of  phos- 
phuretted hydrogen,  they  possess  an  excessively  strong 
stupefying  odour ;  thus  ethyl  phosphine  has  a  perfectly  over- 


120     IV.  DERIVATIVES  OF  THE  MONATOMIC  ALCOHOLS. 

powering  smell,  and  excites  on  the  tongue  and  deep  down  in 
the  throat  an  intensely  bitter  taste. 


Summary. 


Phosphines. 

Phosphontum 
Bases. 

Primary. 

Secondary. 

Tertiary. 

Quaternary. 

(CH,)PH2 

Methyl 
phosphine. 

Gas,  B.  Pt.  -  14° 
Spontaneously 

(CH3),PH 
Di-methyl 
phosphine. 

Liq.,  B.  Pt.  25° 
inflammable. 

(CH3)3P 

Tri-methyl 
phosphine. 

Liq. ,  B.  Pt.  41° 
Fuming. 

(CH3)4PI  and 
(CH3)4P.OH 
Tetra-methyl- 
phosphonium- 
hydroxide. 

Similar  to  potash. 

Yield  upon  oxidatio 
with  fuming  nitric  acid. 

n 

in  the  air. 

Yields 
heating  C 

<  

upon 
H4  and 

(CH3)PO(OH)2 
Methyl- 
phosphonic  acid. 

Like  pa 

M.  Pt.  105° 

(CH3)2PO(OH) 

Di-methyl- 
phosphinic  acid. 

raffin. 

M.  Pt.  76° 

(CH3)3PO 

Tri-methyl- 
phosphine  oxide. 

Hygroscopic 
needles. 

B.  Pt.  240° 

Formation.    1.  The  tertiary  phosphines,  and  also  quaternary  com- 
pounds, result  directly  from  phosphine  and  alkyl  iodide,  in  a  manner 
analogous  to  method  of  formation  2  of  the  amines  : 
PH3  +  3C2H5I  =  P(C2H5)3  +  3HL 

2.  According  to  Hofmann  (1871),  primary  and  secondary  phosphines 
are  formed  by  heating  phosphonium'  iodide  and  alkyl  iodide  with  zinc 
oxide,  e.g.  : 

2C2H5I  + 2PH4l  +  ZnO  =  2P(C2H5)H2,  HI  +  ZnIs  +  HaO. 
They  can  be  separated  from  one  another  by  decomposing  the  salts  of 
the  primary  phosphines  by  water,  as  already  mentioned. 

3.  The  tertiary  phosphines  are  produced  from  calcium  phosphide  and 
alkyl  iodide,  a  reaction  first  observed  by  Thenard  in  1846  ; 


PHOSPHINKS. 


121 


4.  Also  from  phosphorus  trichloride  and  zinc  methyl. 

5.  The  phosphonium  compounds  result  from  the  combination  of 
tertiary  compounds  with  halogen  alkyl,  and  are  very  similar  to  the 
corresponding  ammonium  compounds. 


Methyl  phosphine,  CH3.PH2,  (Hofmann),  is  of  neutral 
reaction  and  easily  soluble  in  alcohol  and  ether;  its  salts 
bleach  vegetable  colours. 

Tri-methyl  phosphine,  P(CH3)3,  changes  in  the  air  into 
Tri-methyl-phosphine  oxide,  P(CH3)30,  which  distils  without 
decomposition  and  is  very  stable  in  character.  The  phosphine 
also  forms  with  sulphur  a  sulphide  analogous  to  the  oxide,  and 
with  chlorine  a  di-chloride,  and  it  combines  with  carbon 
bisulphide  co  a  compound  crystallizing  in  red  plates.  This 
last  reaction  is  very  delicate,  (Hofmann). 

Tri-methyl-phosphonium  Hydroxide,  P(CH3)40H.  Unlike 
the  analogous  ammonium  hydroxide  this  compound  decom- 
poses upon  heating  into  tri-methyl-phosphine  oxide  and 
methane : 

P(CH3)40H  =  P(CH3)30  +  CH^. 

The  tetra-ethyl  compound  breaks  up  in  the  same  way. 

Tri-ethyl  phosphine,  'P{C^'R^)^,  has  no  alkaline  reaction. 
When  concentrated  it  possesses  a  stupefying,  and  when  dilute 
a  pleasant  hyacinth-like  odour. 

The  tendency  of  phosphorus  to  go  over  into  the  pentavalent  state 
shows  itself  in  characteristic  fashion  in  these  compounds.  The  group 
P(CH3)4  is  a  strongly  positive  monovalent,  and  the  group  P(CH3)3  a 
strongly  positive  divalent  radicle,  the  former  being  comparable  with  the 
alkalies  and  the  latter  with  the  alkaline  earth  metals.  The  metalloid 
character  of  phosphorus  is  therefore  changed  into  one  more  metallic  by 
the  advent  of  the  alkyl  groups. 

The  phosphonic  acids,  phosphinic  acids  and  phosphine  oxides  above- 
mentioned  can  be  derived  from  phosphoric  acid  by  the  exchange  of  OH 
for  alkyl,  thus  : 

rOH  ecu,  (C2H5  (C,H, 

PO^OH  PO-^OH  PO-^CoHs  PO^C.Hg 

[oh  iOH  iOH  [C^llr, 

Phosphoric    Ethyl-phosphonic  Di-ethyl-phosphinic  Tri-ethyl- 
acid.  acid.  acid.         phosphine  oxide. 


122     IV.  DERIVATIVES  OF  THE  MON ATOMIC  ALCOHOLS. 


The  first  may  also  be  regarded  as  alcoholic  derivatives  of  phosphor- 
ous and  hypopliosphoroiis  acids,  but  not  as  ethers  of  these,  since  they 
are  not  saponifiable. 


2.  Arsenic  Compounds  of  Alcohol  Radicles. 


Type.  1 

Arsines. 

Arsonium  Bases. 

Primary. 

Secondary. 

Tertiary. 

Quaternary. 

CO 

o 

Methyl -arsine 

dichloride. 
Liq.,B.Pt.  133° 

AsCl(CH3)2 
Cacodyi 
chloride 
Liq.,  B.  Pt.  100° 

As(CH3)3 
Tri-methyl 
arsine. 
,  Liq.,  B.  Pt.  70° 

As(CH3)4 .  OH 
Tetra-methyl- 
arsone  hydroxide; 
like  potash. 
As(CH3)4l 
Tetra-methyl- 
arsone  iodide. 
Tables. 
As(CH3)4Cl 
Tetra-methyl- 
arsone  chloride. 

O 

< 

Chlori 

AsCyCHg) 
Methyl-arsine- 
tetrachloride. 

ne  Addition-com 

AsCl3(CH3)2 

Cacodyi 
trichloride. 

30unds. 

AsCl2(OH3)3 
Tri-methyl- 
arsine  dichloride 

Corresponding  Oxides. 

eo 

o 

m 
< 

As(CH3)0 
Methyl-arsine 

oxide. 
Prisms,  M.  Pt. 
95° 

fAs(CH3)j20 
Cacodyi  oxide. 

Liquid,  B.  Pt. 
150° 

CO 

w 

o 
o 

< 

(CH3)AsO(OH)2 
M  ethyl- arsonic 
acid. 
Tables. 

(CH3)2AsO(OH) 
Cacodylic  acid. 
Prisms,  M.  Pt. 
200° 

(CH3)3AsO 
Tri-methyl - 
arsine  oxide. 
Crystals. 

The  similarity  of  arsenic  to  phosphorus  and  nitrogen  is 
further  exemplified  by  the  analogous  compounds  which  it 
forms  with  alcohol  radicles.  In  virtue,  however,  of  the  more 
metallic  character  of  arsenic,  these  compounds  differ  from  the 
others  by  the  arsenic  not  being  able  to  combine  with  hydrogen 


ARSENIC  COMPOUNDS. 


123 


together  with  alcohol  radicles,  but  only  with  electro-negative 
elements  like  chlorine  or  oxygen.  Arsenic  analogues  of 
methylamine  and  di-methylamine  have  therefore  no  existence, 
but  we  know  tri-methyl-arsine,  analogous  to  tri-methylamine 
and  tri-methyl-phosphine.  As  primary  and  secondary  com- 
pounds we  have  methyl-arsine  dichloride,  CH3.ASCI2,  di- 
methyl-arsine  chloride,  (CH3)2=AsCl,  and  analogous  sub- 
stances. 

They  are  colourless  liquids  of  stupefying  odour,  exerting 
in  some  cases  an  unbearable  irritating  action  upon  the  mucous 
membrane.  They  do  not  possess  basic  properties.  In 
addition  to  these  there  exist  also  quaternary  compounds  which 
are  exactly  analogous  to  the  quaternary  phosphonium  ones. 

The  halogen  of  the  chlorine  compounds  is  easily  replaceable 
by  its  equivalent  of  oxygen.  Thus,  corresponding  to  the 
compound  R.ASCI2  there  is  an  oxide  R.AsO  and  a  sulphide 
E.AsS,  and  to  the  chloride  RgAsCl  an  oxide  (R2As)20. 
(See  tabular  summary,  row  3.)  These  oxides,  liquid  or  solid, 
are  compounds  of  stupefying  odour,  and  behave  like  basic 
oxides ;  hydrochloric  acid  reconverts  them  into  the  chlorides. 

Here,  also,  the  tendency  of  arsenic  to  change  from  the — 
(apparently) — trivalent  to  the  pentavalent  state  is  especially 
marked.  The  above  chlorides  and  tri-methyl-arsine  itself  all 
combine  with  two  atoms  of  chlorine  to  compounds  of  the  type 
AsX^,  (see  table,  row  2).  The  above  oxygen  compounds  of  the 
type  AsXg  and  also  tri-methyl-arsine  are  consequently  oxidiz- 
able  to  compounds  containing  one  0-atom  or  two  OH-groups 
more,  acids  or  oxides  which  are  also  formed  from  the  chlorides 
of  the  type  AsX^  by  exchange  of  halogen  for  0  or  OH,  e.g. 
cacodyl  oxide,  (R2As)20,  to  cacodylic  acid,  RgAs.OOH,  (see 
table,  row  4).  These  products  are  therefore  completely 
analogous  to  the  phosphonic  and  phosphinic  acids  and 
phosphine  oxides  already  described. 

The  compounds  As(CH3)xCl5_^,  of  the  type  AsX^,  break 
up  upon  heating  into  methyl  chloride  and  compounds 
As(CH3)x_iCl4_3„  of  the  type  ASX3,  this  separation  of  methyl 
chloride  taking  place  the  more  readily  the   fewer  methyl 


124     IV.  DERIV^ATIVES  OF  THE  MON  ATOMIC  ALCOHOLS, 

groups  are  present  in  the  molecule ;  thus  As(CH3)3Cl2  breaks 
up  when  somewhat  strongly  heated,  As(CH3)2Cl3  at  50°,  and 
As(CH3)Cl4  at  0°,  i.e.  the  last-named  is  only  stable  when  in 
a  freezing  mixture.  When,  therefore,  chlorine  acts  upon 
As(CH3)Cl2  at  the  ordinary  temperature,  the  reaction  appears' 
to  be  one  of  direct  exchange  of  alkyl  for  chlorine,  thus  ; 

AS(CH3)C12  +  Cl2   =   ASCI3  +  CH3CI. 

If  one  considers  arsenic  to  be  a  trivalent  element,  one  finds  support 
for  this  view  in  the  fact  of  AsClg  having  no  existence,  and  As(CH3)g  only 
a  doubtful  one  ;  the  compounds  of  the  type  AsXg  are  in  this  case  to  be  re- 
regarded  as  molecular  compounds  of  ASX3+  Clg.  The  adding  on  of  the 
chlorine  molecule  would  thus  be  conditioned  by  the  latent  affinities  of  the 
chlorine  to  the  arsenic  and  to  the  alcohol  radicle,  which  indeed  finds 
expression  in  the  separation  of  chloro-alkyl  at  an  increased  temperature. 

Of  especial  interest  is  the  existence  of  the  isolated  radicle 
cacodyl,  As(CH3)2,  which  in  the  free  state  has  the  formula 
As2(CH3)4,  i.e.  it  is  di-arsene  tetra-methyl. 

Modes  of  formation.    A.  The  tertiai^y  arsines  result : 

1.  From  sodium  arsenide  and  alkyl  iodide,  {Cahours  and  Riche), 

AsNag  +  SCgHgl  =  As(C2H5)3  +  3NaI. 

2.  From  zinc  alkyl  and  arsenic  trichloride,  {Hofmann), 
Tri-methyl-arsine,  AslCHgjg,  and  tri-ethyl-arsine,  As(C2H5)3,  are 

liquids  difficultly  soluble  in  water.  They  fume  in  the  air,  changing 
thereby  into  tri-methyl-  or  -ethyl- arsine  oxide,  with  evolution  of  heat. 

B.  The  secondary  arsines  are  obtained  from  cacodyl  and 
cacodyl  oxide,  which  result  from  the  distillation  of  potassium 
acetate  and  arsenic  trioxide,  (Cadet,  1760) : 

0{ig  +  4CH,C0,K  =  0{i«™;  +  2C0,.2C03K, 

The  distillate  of  cacodyl  and  cacodyl  oxide  so  obtained,  and 
termed  "  alkarsin,"  fumes  in  the  air  and  is  spontaneously  in- 
flammable, "fuming  arsenical  liquid.")  Hydrochloric 
acid  acts  upon  it  to  form  cacodyl  chloride  {Bunsen,  1838),  and 
caustic  potash  solution  gives  pure  Cacodyl  oxide,  As2(CH3)40,  a 
liquid  of  stupefying  odour  which  produces  nausea  and  unbear- 
able irritation  of  the  nasal  mucous  membrane  ;  it  boils  without 
decomposition,  and  is  insoluble  in  water  and  of  neutral  reaction. 


ANTIMONY  COMPOUNDS,  ETC. 


125 


It  yields  salts  with  acids,  e.g.  Cacodyl  chloride  with  hydro- 
chloric acid : 

{(CH3)2As}20  +  2HC1  =  2(CH3)2As.Cl  +  H^O. 

This  latter  compound  is  a  liquid  of  even  more  stupefying 
odour  and  violent  action  than  the  former,  and  whose  vapour 
is  spontaneously  inflammable.  Upon  being  heated  with  zinc 
clippings  in  an  atmosphere  of  carbonic  acid,  it  yields  the  free 
Cacodyl,  As2(CH3)4  (from  /<aKco8^?,  "stinking"),  a  colourless 
liquid  insoluble  in  water  and  boiling  undecomposed  at  170°, 
of  a  horrible  nauseous  odour  which  produces  vomiting.  It  is 
as  easily  inflammable  in  the  air  as  the  vapour  of  phosphorus, 
yielding  the  oxide  when  slowly  brought  in  contact  with  it, 
and  also  combining  directly  with  sulphur,  chlorine,  etc. 
Cacodyl  plays,  therefore,  even  down  to  the  most  minute  par- 
ticulars, the  role  of  a  simple  electro-positive  element ;  it  is  a 
true    organic  element,"  (Btmsen), 

Cacodylic  acid,  (CH3)2AsO.OH,  is  crystalline,  soluble  in 
water,  odourless  and  poisonous.    It  forms  crystallizable  salts. 

C.  The  primary  arsines  or  mono-alkyl-arsenic  compounds(5ae2/er,1858), 
result  from  Alkyl-arsine  dichloride,  e.g,  CHgAsClg,  which  on  its  part  is 
obtained  by  heating  cacodyl  trichloride,  with  separation  of  CH3CI.  It 
is  a  heavy  liquid,  soluble  in  water  without  decomposition,  and  also 
boiling  undecomposed,  its  vapour  having  a  terribly  aggressive  action. 

3.  Antimony,  Boron,  and  Silicon  compounds. 

Antimony  also  forms  compounds  with  the  alkyls  precisely  similar  to 
those  of  arsenic ;  primary  and  secondary  compounds  do  not  exist.  Tri- 
methyl-stibine,  Sb(CH3)3  (LandoU),  is  a  highly  disagreeable  and  spon- 
taneously inflammable  liquid  of  onion-like  smell ;  and  Antimony  penta- 
methyl,  Sb(CH3)  g,  an  oily  liquid  of  weak  odour,  which  can  be  distilled, 
and  is  not  spontaneously  inflammable.  Tetra-methyl-stibonium- 
hydroxide,  Sb(CB3)40H,  is  also  very  like  caustic  potash. 

Boron  tri-ethyl,  Bo(C2H5)3  {Frankland),  is  a  spontaneously  inflam- 
mable liquid  which  burns  with  a  green  flame  with  deposition  of  much 
soot,  and  Boron  tri-methyl,  £0(0113)3,  an  analogous  gas  of  an  unbearable 
stinking  smell. 

The  Silicium  compounds  {Friedel  and  Crafts)  are,  in  contradistinction 
to  the  foregoing,  not  like  the  easily  spontaneously  inflammable  silicon 
hydride,  but  like  methane  and  the  paraffins,  and  are  very  stable  in  the 
air,  i.e,  not  spontaneously  inflammable. 


126     IV.  DERIVATIVES  OF  THE  MONATOMIC  ALCOHOLS. 

Silicium  tetra -methyl,  Si(CH3)4,  is  a  mobile  liquid  similar  to  pentane, 
which  swims  upon  water. 

F.  Metallic  Compounds  of  the  Alcohol  Radicles. 

The  alcohol  radicles  can  be  combined  with  almost  all  the 
more  important  metals.  The  composition  of  the  compounds 
so  formed,  termed  organo-metallic  or  metallo-organic  com- 
pounds, almost  always  corresponds  with  that  of  the  metallic 
chlorides  from  which  they  are  derived  by  the  replacement  of 
halogen  by  alkyl.  They  are  colourless  mobile  liquids  which 
boil  without  decomposition  at  relatively  low  temperatures; 
they  often  decompose  violently  with  water  and  burn  explos- 
ively in  the  air,  but  in  other  cases  they  are  stable,  both  in 
water  and  air.  To  the  former  category  belong  the  magnesium, 
zinc  and  aluminium  alkyls,  and  to  the  latter  the  mercury,  lead 
and  tin  compounds. 

Compounds  are  also  known  which  contain  halogen  as  well 
as  alcohol  radicle  combined  with  a  metal.  They  behave  like 
salts.  The  halogen  in  them  can  be  replaced  by  hydroxy], 
whereby  basic  compounds  result,  compounds  which  are  often 
much  more  strongly  basic  than  the  corresponding  metallic 
hydroxides,  in  accordance  with  the  electro-positive  character 
of  the  alcohol  radicle.  Such  hydroxides  or  oxides  cannot  be 
volatilized  without  decomposition. 

Modes  of  formation.  1.  By  treating  the  halogen-alkyl  with 
the  metal  in  question.  In  this  way  zinc-,  magnesium-  and 
mercury-alkyl  are  got : 

Mg,  +  2CH3l  =  Mg(CH3),  +  MgI,. 

2.  By  treating  zinc-alkyl  or  mercury-alkyl  with  the  metal.  One  thus 
obtains  e.g.  cadmium  ethide  and  potassium  methide  : 

Hg(CH3)2  +  Cd  =  Ocl(CH3)2  +  Hg. 

3.  By  double  decomposition  between  zinc-alkyl  and  the  chloride  of 
the  metal : 

2Zn(C2H5)2  +  SnCl4  =  Sn(C2H5)4  +  2ZnCl2. 


Potassium-  and  Sodium  methide,  K(CH3)  and  Na(0H3),  and 
Potassium-  and  Sodium  ethide,  and  Na(C2H5),  are 


ORGANO-METALLIC  COMPOUNDS. 


127 


not  known  in  the  free  state.  When  metallic  sodium  is  added 
to  zinc  ethyl  (or  ethide),  zinc  separates  out  and  a  crystalline 
compound  of  sodium  ethide  and  zinc  ethide  is  formed,  from 
which,  however,  the  former  cannot  be  prepared  pure,  since 
decomposition  sets  in  upon  warming.  On  distilling  in  a  stream 
of  carbonic  acid,  the  potassium  methide  combines  with  the 
latter  to  form  potassic  acetate ;  the  ethyl  compound  behaves 
in  a  similar  way. 

Zinc  methyl  or  methide,  Zn(CH3)2,  {Frankland,  1849). 
This  important  compound  is,  like  the  other  zinc  alkyls,  pre- 
pared according  to  method  1,  the  reaction  taking  place  in  two 
stages  : 

I.  CH3I  +  Zn  =  Zn(CH3l) ; 
11.  2Zn(CH3)I  =  Zn(CH3)2  +  Znl^. 

The  first  stage  is  completed  upon  warming,  and  the  second 
upon  distilling  the  resulting  product.  The  zinc  is  conveniently 
used  in  the  form  of  the  "  copper-zinc  couple,"  and  the  reaction 
is  facilitated  by  the  addition  of  acetic  ether,  the  reason  for  this 
not  being  known.  Zinc  methyl  is  a  colourless,  mobile,  strongly 
refracting  liquid  of  very  piercing  and  repulsive  smell. 
B.  Pt.  46° ;  Sp.  Gr.  1*39.  It  takes  fire  in  the  air  at  once,  and 
burns  with  a  brilliant  reddish-blue  flame  (the  zinc  flame),  with 
formation  of  zinc  oxide.  When  the  supply  of  oxygen  is 
limited,  zinc  methylate,  Zn(OCH3)2,  is  formed.  It  decomposes 
violently  with  water  to  methane  and  Zn(0H)2,  and  gives  ethane 
with  methyl  iodide.  It  is  employed  e.g.  in  the  preparation 
of  secondary  and  tertiary  alcohols  and  of  acetone.  Iodine 
converts  it  into  Zinc-methyl  iodide,  ZnCH3l,  white  plates, 
(see  above),  and  methyl  iodide ;  an  excess  of  iodine  yields 
zinc  iodide  and  methyl  iodide. 

Zinc  ethide,  Zn(C2H5)2,  B.  Pt.  118°,  Sp.  Gr.  M8,  is  exactly 
like  zinc  methide. 

Mercury  methide,  Hg(CH3)2,  (FranJdand)^  and  Mercury  ethide, 
Hg(C2H5)2,  {Bnckton)y  are  produced  by  method  of  formation  1,  also 
by  method  3.  They  are  colourless  liquids  of  peculiar  sweetish  and 
unpleasant  odour.  B.  Pt.  of  the  methyl  compound  95°,  and  Sp. 
Gr.  :>3.  B.  rt.  of  the  ethyl  compound  159".  They  are  permanent 
in  the  air  but  inflammable,  and  both — especially  the  methyl  compound— 


128 


V,  ALDEHYDES  AND  KETONES. 


are  very  poisonous.    HCl  reacts  to  produce  Mercury-methyl  chloride, 

Hg(CH3)Cl,  a  colourless  salt,  thus  : 

Hg(CH3)2  +  HCl  =  Hg(CH3)Cl  +  CH4. 

To  this  there  is  a  corresponding  iodide  and  also  a  hydroxide, 
Hg(CH3)0H,  of  strongly  alkaline  reaction. 

Mercury-ethyl  hydroxide,  Hg(C2H5)OH,  is  an  oily  odourless  liquid  of 
extremely  caustic  taste,  slippery  to  the  touch  like  potash,  and  gradually 
blistering  the  skin. 

Aluminium  methide,  A1(CH3)3,  is  spontaneously  inflammable  and 
decomposes  violently  with  water. 

Lead  methide,  Pb(CH3)4,  and  ethide,  Fh{C2H.Q) 4  {Cahours).  These  are 
formed  according  to  method  3,  curiously  with  separation  of  lead  : 

2PbCl2  +  2Zn(CH3)2  =  Pb(CH3)4  +  Pb  +  2ZnCl2. 
They  are  stable  in  the  air,  and  are  interesting  from  the  lead  in  them 
being  tetravalent.  The  Hydroxide,  Pb(CH3)3.0H,  forms  pointed 
prisms,  smells  like  mustard,  and  is  a  strong  alkali ;  thus,  it  saponifies 
fats,  drives  out  ammonia  from  its  salts,  precipitates  metallic  salts,  etc. 
The  compound  Pb2(C2H5)g  is  also  known. 

The  tin  compounds  are  similar  (Ladenhurg,  Frankland), 
Tin  tetra-methide,  Sn(CH3)4,  Tin  tetra- ethide,  Sn(C2H5)4,  Tin  tri- 
ethide,  Sn2(C2Hg)g,  Tin  di-methide,  Sn2(CH3)4,  etc.,  are  of  interest  as 
proving  the  tetravalence  of  tin. 


V.  ALDEHYDES  AND  KETONES,  aH^^O. 

The  aldehydes  and  ketones  are  substances  which  result  from 
the  oxidation  of  the  primary  and  secondary  alcohols  respec- 
tively, with  separation  of  two  atoms  of  hydrogen. 

The  Aldehydes  are  formed  from  the  primary  alcohols,  and 
are  easily  converted  by  further  oxidation  into  the  correspond- 
ing acids  containing  an  equal  number  of  carbon  atoms,  oxygen 
being  taken  up.  They  possess  in  consequence  strongly  re- 
ducing properties. 

The  Ketones  result  from  the  oxidation  of  the  secondary 
alcohols,  and  are  more  difficult  to  oxidize  further;  they  do 
not  possess  reducing  properties.  Their  oxidation  does  not 
lead  to  acids  containing  an  equal  number  of  carbon  atoms  in 
the  molecule,  but  to  others  containing  a  smaller  number,  the 
carbon  chain  being  broken. 


ALDEHYDES. 


129 


The  lower  members  of  both  classes  are  neutral  liquids  of 
peculiar  smell,  easily  soluble  in  water  and  readily  volatile, 
only  CH2O  being  gaseous.  With  increasing  carbon  they  soon 
become  insoluble  in  water,  and  their  odour  becomes  less 
marked  with  rise  of  melting  point  until  the  highest  members 
are  solid,  odourless,  like  paraffin,  and  only  capable  of  being 
distilled  without  decomposition  in  a  vacuum. 

The  aldehydes  are  also  perfectly  analogous  to  the  ketones  as 
regards  other  modes  of  formation  and  in  many  of  their  pro- 
perties. 

A.  Aldehydes. 

The  homologous  series  of  the  aldehydes,  CnHgi^O,  corre- 
sponds exactly  with  that  of  the  acids,  CiiH2ij02.  Their  boiling 
points  lie  decidedly  lower  than  those  of  the  corresponding 
alcohols,  and  rise,  in  the  normal  aldehydes,  at  first  by  about 
27°  for  each  CHg,  and  later  on  by  a  less  amount. 

Modes  of  formation.  1.  By  the  regulated  oxidation  of  the 
primary  alcohols,  CnHsn+iOH,  by  potassium  bichromate  or 
manganese  dioxide  and  dilute  sulphuric  acid ;  often  slowly  by 
the  oxygen  of  the  air  alone,  especially  in  the  presence  of  bone 
black  or  platinum  : 

CH3.CH2OH  +  0  =  CH3.CHO  +  H2O. 

Alcohol.  Acetic  aldehyde. 

Aldehydes  are  also  produced  by  the  oxidation  of  many 
complicated  organic  substances,  such  as  albumen. 

2.  From  the  acids  of  the  acetic  series,  by  distilling  a  mixture 
of  their  calcium  or  barium  salts  with  calcium  or  barium 
formate,  {Limpricht).    The  formic  acid  acts  in  this  instance  as 
a  reducing  agent,  producing  calcium  carbonate,  thus  : 
CHg.COOca  +  HCOOca  =  CH3.CHO  +  CaC03.    (ca  -  i  Ca.) 

Other  reducing  agents  have  for  the  most  part  no  action. 

3.  From  the  di-halogen  substitution  products  of  the  hydro- 
carbons containing  the  atomic  group  CHX2,  by  superheating 
with  water  or  by  boiling  with  water  and  PbO  : 

CHg—CHCl^  +  H2O  =  CH3— CHO  +  2HC1. 

Ethylidene  chloride. 

( 51V6 )  I 


130 


V.  ALDEHYDES  AND  KETONES. 


Constitution.  By  the  oxidation  of  the  primary  alcohols, 
E — CH2.OH,  to  their  corresponding  acids,  whose  constitution 
follows  as  R — CO. OH,  the  new  oxygen  atom  affixes  itself 
only  to  that  carbon  atom  which  is  already  combined  with 
oxygen — in  the  form  of  hydroxyl — ,  the  hydrocarbon  radicle 
R  remaining  unaltered.  It  must  consequently  also  remain 
unchanged  in  the  intermediate  products  of  the  oxidation,  the 
aldehydes,  which  therefore  possess  the  constitution  R — CHO : 

CH3— CH2.OH        CH3— CHO        CH3— CO.OH 
Alcohol.  Aldehyde.  Acetic  acid. 

The  aldehydes  thus  contain  the  atomic  group  — CHO  or 
— ^^H'  either  to  hydrogen  as  in  formic  aldehyde, 

H — CHO,  or  to  an  alcohol  radicle  as  in  all  the  other  cases. 

Isomers.  Isomerism  in  the  aldehydes  is  caused  solely  by 
isomerism  in  the  alcohol  radicles  R,  which  are  combined  in 
them  with  the  group  — CHO,  and  therefore  contain  an  atom 
of  carbon  less.  Otherwise  the  aldehydes — from  C3HgO  on — 
are  isomeric  with  the  ketones,  with  the  oxides  of  the  olefines 
{e.g.  aldehyde  with  ethylene  oxide,  C2H4O),  and  with  the 
alcohols  of  the  ally  lie  series. 

Behaviour.  The  aldehydes  are  distinguished  by  being 
exceptionally  active  chemically. 

1.  For  oxidation,  see  above.  The  aldehydes  are  very 
readily  oxidizable,  slowly  even  by  the  air  alone,  and  quickly 
by  chromic  acid,  salts  of  the  noble  metals,  etc.  They  conse- 
quently reduce  an  ammoniacal  solution  of  silver  and  often  one 
of  copper;  this  reaction  is  characteristic  and  is  especially 
delicate  in  the  presence  of  caustic  soda  solution. 

2.  The  aldehydes  are  easily  reducible  by  nascent  hydrogen, 
e.g.  sodium  amalgam  and  dilute  acid  or  zinc  dust  and  glacial 
acetic  acid,  to  the  primary  alcohols  from  which  they  are 
derived  by  oxidation,  e.g.  : 

CH3-CHO  +  H2  =  CH3.CH2OH. 

A  glycol  is  formed  as  intermediate  product,  e.g.  butylene 
glycol,  C4Hs(OH)2,  from  G^Rfi, 


ALDEHYDES;  BEHAVIOUR  OF. 


131 


3.  Phosphorus  pentachloride  and  -trichloride  convert  the 
aldehydes  into  ethylidene  chloride  and  analogous  di-chloro- 
substitution  products  of  the  hydrocarbons. 

4.  Addition-reactions.  One  would  expect  that  upon  treat- 
ing ethylidene  chloride  or  analogous  chlorides  with  water  and 
lead  oxide,  for  instance,  two  hydroxyl  groups  would  replace 

OH 

two  chlorine  atoms,  and  a  compound,  CH3 — CH<^qjj,  would 

be  produced,  which  would  be  a  diatomic  alcohol,  ethylidene 
glycol."  Such  compounds  are  however  not  formed,  being 
apparently  broken  up  at  once  into  aldehyde  and  water,  thus  : 

CH3— CH<Qg  =  CH3— CHO  +  H2O. 

From  this  we  may  draw  the  conclusion  that  two  hydroxyl 
groups  hound  to  one  and  the  same  carbon  atom  cannot  as  a  rule  exist 
together,  but  a  molecule  of  water  is  separated,  and  an  oxygen 
atom  is  bound  by  its  two  affinities  instead.  Only  in  particular 
cases  are  compounds  with  two  such  hydroxy  Is  capable  of 
existence  (see  below),  being  formed  by  the  addition  of  water 
to  the  aldehyde  in  question. 

If,  in  place  of  water,  NaHS03,  NH3,  HON,  etc.,  be  employed, 
direct  addition  to  the  aldehydes  is  observed,  and  this  is  to  be 
explained  in  every  case  by  the  doubly-linked  oxygen  atom 
loosening  one  of  its  affinities  from  the  carbon,  so  that  an 
affinity  remains  free  in  the  case  of  both  of  them,  thus  : 

CH3— CH<^"~,  or,  generally,  R— CH<^"~. 

A  hydrogen  atom  of  the  substance  in  question  now  affixes 
itself  to  the  oxygen  of  the  aldehyde,  with  formation  of  a 
hydroxyl  group,  while  the  residual  X,  e.g.  NH2,  which  was 
originally  bound  to  the  afore-mentioned  H-atom,  attaches 
itself  to  the  carbon;  these  compounds  receive  therefore  the 
formula : 

CH3— 0H<§^  . 

The  substances  so  p>roduced  are  to  be  regarded  as  deriva- 
tives, such  as  simple  and  compound  ethers,  amines,  etc.,  of  the 
hypothetical  ethylidene-  and  homologous  glycols. 


132 


V.  ALDEHYDES  AND  KETONES. 


The  most  important  addition-reactions  are  as  follows :  — 

{a)  Combination  with  water,  which  would  lead  to  a  diatomic 
alcohol,  does  not  as  a  rule  take  place,  for  the  reasons  already 
given.  Should  the  alcohol  radicle  of  the  aldeh^^de,  however, 
contain  several  negative  atoms,  e.g.  CI,  then  the  hydrates  are 
capable  of  existence,  for  instance  chloral  hydrate  : 

CCI3— CHO  +  H2O  =  CCI3— CH(0H)2. 

But  even  in  these  cases  the  tendency  for  water  to  separate 
is  too  great  to  allow  of  such  hydrates  behaving  as  diatomic 
alcohols ;  they  react  rather,  for  the  most  part,  exactly  like  the 
aldehydes  themselves.    (Cf.  pyroracemic  and  mesoxalic  acids.) 

(&)  Similarly,  combination  but  seldom  takes  place  with 
alcohol,  acetic  acid,  etc.,  with  the  formation  of  an  easily  decom- 
posable alcoholate  or  acetate.  But,  upon  heating  with  alcohol 
or  acetic  anhydride,  stable  ethers,  simple  and  compound,  of  the 
hypothetical  glycols  are  obtained  : 

CH3— CHO  +  2C2H,.OH  =  CH3— CH(OC2H,)2  +  H^O. 

CH3— CHO  +  (C^HgO)^  =  CH3— CH(OC2H302). 

The  compounds  resulting  from  alcohols,  the  so-called 
*'acetals"  (see  p.  136),  are  also  formed  by  the  partial  oxidation 
of  primary  alcohols,  and  are  again  separated  into  their  com- 
ponents by  sulphuric  acid. 

Thio-alcohols  (p.  93),  yield  with  aldehyde,  under  the  influence  of 
gaseous  HCl,  thio-acetals  which  are  termed  Mercaptals. 

{c)  The  aldehydes  combine  with  sodium  bisulphite,  NaHSOg, 
ammonium  bisulphite,  etc.,  to  crystalline  compounds,  easily 
soluble  in  water  but  difficultly  in  alcohol,  e.g, 
C2H4O  +  NaHSOg  +  IH2O. 
These  are  to  be  regarded  as  sulphonic  acids  of  the  ethy- 
lidene-  etc.,  glycols,  for  instance,  CH3 — CH(0H)(S03Na). 
Nevertheless  they  are  almost  always  easily  broken  up  again 
with  re-formation  of  the  aldehyde,  warming  with  soda  solution 
or  with  acids  effecting  this.  They  are  therefore  of  great  im- 
portance for  the  separation  of  aldehydes  from  mixtures. 

{d)  The  aldehydes  combine  with  ammonia  to  aldehyde- 
ammonias,  e.^. Aldehyde-ammonia,  CH3 — CH(0H)(NH2).  These 


ALDEHYDES;  BEHAVIOUR  OF. 


133 


are  crystalline  compounds,  for  the  most  part  easily  soluble  in 
water,  difficultly  in  alcohol,  and  insoluble  in  ether,  whicli  go 
back  into  the  original  aldehyde  when  warmed  with  dilute 
acids.  Like  the  bisulphite  compounds,  they  are  advantageously 
used  for  the  preparation  of  pure  aldehydes.    (See  p.  135.) 

Imido-compounds  of  the  aldehydes,  R — CH=NH,  are  only  known  hi 
a  few  instances,  e.g.  chloral-imide,  CCI3 — CH=NH ;  ethyl-rnethylene- 
amine,  CHg^N — C.2H5,  from  ethylamine  and  tri-oxy -methylene  (p.  135). 

Many  nitrile  compounds  are  known,  e.g.  Hydracetamide,  (CH3-CH)3N2. 

{e)  The  aldehydes  combine  with  hydrocyanic  acid  to  form 
nitriles  of  higher  acids,  thus,  acetic  aldehyde  yields  the  com- 
pound CH3 — CJ*<^Q^,  ethylidene  cyanhydrin,  a  liquid  easily 

broken  up  again  into  its  components.    (See  lactic  acid.) 

5.  The  aldehydes  show  great  tendency  to  polymerize.  (See 
pp.  13  and  48.)  In  the  case  of  formic  aldehyde  this  poly- 
merization sets  in  of  its  own  accord  at  the  ordinary  temperature. 
Acetic  aldehyde  is  polymerized  upon  the  addition  of  small 
quantities  of  hydrochloric,  sulphuric,  or  sulphurous  acid,  zinc 
chloride,  carbonyl  chloride,  etc.,  to  para-aldehyde,  CgH^gOs? 
=  (021340)3,  at  the  ordinary  temperature,  and  to  meta-alde- 
hyde,  at  0°.  Why  the  above-mentioned  substances 
should  induce  this  polymerization  is  not  known. 

6.  Towards  alkalies  the  aldehydes  behave  differently.  Alde- 
hyde and  several  of  its  homologues  are  converted  by  heating 
with  caustic  soda  solution  into  a  reddish-brown  resin  termed 
aldehyde-resin,  insoluble  in  water  but  soluble  in  alcohol,  a 
peculiar  odour  being  apparent  at  the  same  time.  This  reaction 
is  characteristic.  Other  aldehydes  are  transformed  by  alkalies 
into  a  mixture  of  equal  molecules  of  alcohol  and  acid,  the  one 
half  being  oxidized  at  the  cost  of  the  other  half,  thus  : 

2HC0H  =  CH3OH  4-  H.CO2H. 

Formic  acid. 

7.  The  aldehydes  show  great  inclination  to  form  condensa- 
tion products,  i.e.  two  molecules  may  combine  together  with  a 
rearrangement  of  the  carbon  bonds  and  formation  of  a  com- 
pound containing  twice  as  many  atoms  of  carbon,  a  hydrogen 


134 


V.  ALDEHYDES  AND  KETONES. 


atom  of  the  one  molecule  combining  with  the  oxygen  of  the 
other  to  hydroxyl. 

In  this  way,  when  aldehyde  stands  for  a  lengthened  period 
with  dilute  hydrochloric  acid,  /?.  oxy-butyric  aldehyde  (see 
Aldol)  is  formed : 

CH3— CHO  +  CH2H— CHO  =  CH3— CH(OH)— CH2— CHO. 

Aldol  condensation,  Aldol  readily  separates  water  and  goes  into 
Crotonic  aldehyde,  CH3— CH=CH— CHO,  which  also  results  directly 
upon  warming  aldehyde  with  zinc  chloride,  (Aldehyde  condensation). 
Sulphuric  acid,  sodium  acetate  in  aqueous  solution,  and  alkalies,  e.g. 
dilute  soda,  baryta  water,  etc. ,  also  induce  condensation. 

The  "aldol  condensation"  is  easily  explained  by  assuming  the  for- 
mation of  an  aldehyde  hydrate,  and  subsequent  separation  of  one  of  the 
two  hydroxyls  thus  formed  with  a  hydrogen  atom  of  a  second  aldehyde 
molecule.    For  condensation  with  ketones,  see  these. 

7a.  The  aldehydes  combine  in  a  similar  manner  with  sodium  acetate 
and  acetic  anhydride  to  acids  poorer  in  hydrogen,  See  .e.g'.  cinnamic 
acid. 

8.  Chlorine  and  bromine  act  upon  the  aldehydes  as  sub- 
stituents  ;  thus,  from  acetic  aldehyde  chloral  is  obtained  , 

CH3— CHO  +  3CI2  =  CCI3— CHO  +  3HC1. 

9.  Sulphuretted  hydrogen  converts  the  aldehydes  into  thio-aldehydes. 
These  are  compounds  of  unpleasant  aromatic  odour,  which  show  the 
same  peculiarities  of  polymerization  as  the  aldehydes,  (Klinger,) 

10.  With  hydroxylamine  the  aldehydes  yield  the  so-called 
Aldoximes,  water  being  separated,  e.g.  aldoxime, 

CH3— CH=N.OH,  {V.  Meyer,  B.  15,  2778). 

CH3.CHO  +  NH2OH  =  CH3.CH=:N.0H  +  H2O. 

The  aldoximes  are  liquids  which  distil  for  the  most  part  without  de- 
composition, are  capable  of  forming  simple  and  compound  ethers  in 
virtue  of  their  hydroxyl  hydrogen,  and  are  broken  up  into  their  com- 
ponents upon  boiling  with  acids.  Acetic  anhydride  decomposes  them  for 
the  most  part  into  nitrile  and  water  : 

CH3— CH=N.OH  =  CH3.CN  +  H2O. 

By  the  reduction  of  the  oximes,  primary  amines  result,  (p.  113* 
Qoldschmidt,  B.  19,  3232;  20,  728)  : 

CH3— CH  :  N.OH  +  2H2  =  CH3-CH2— NH2  +  H2O. 

Y  ^  

Aldoxime.  Ethylamine. 


ALDEHYDE. 


135 


11.  The  analogous  reaction  follows  still  more  easily  in  the  case  of 
phenyl-hydrazine  than  in  that  of  hydroxylamine,  {E.  Fischer). 

E— CHO  +  CeHg— NH-NH2  =  R— CH=N— NH— CgHg  +  H,0. 

The  compounds  which  are  formed  in  this  way  are  termed  Hydrazones 
or  Hydrazides.    (For  further  details,  see  p.  373. ) 

Tests  for  aldehydes.  (1)  Behaviour  with  ammoniacal  silver 
solution  (see  p.  130,  and  also  B.  15,  1629).  (2)  Behaviour 
with  alkaline  bisulphites  (see  p.  132).  (3)  Behaviour  with 
phenyl-hydrazine  and  hydroxylamine.  (4)  Aldehydes  colour 
a  fuchsine  solution,  which  has  been  decolourized  by  sulphurous 
acid,  an  intensive  violet-red;  some  ketones  and  chloral,  but 
not  chloral  hydrate,  produce  the  same  effect.  Schiff,  Caw. 
(B.  13,  2343). 

Formic  Aldehyde,  Methyl  Aldehyde,  H.CHO.  This  may 
also  be  regarded  as  the  oxide  of  the  diatomic  radicle  methy- 
lene, CH2=.  It  is  obtained  dissolved  in  excess  of  methyl 
alcohol  by  leading  the  vapour  of  the  latter,  mixed  with  air, 
over  a  glowing  platinum  or  copper  spiral  or  platinum  asbestos, 
{Hofmann,  1869).  Other  oxidizing  agents  lead  directly  to 
formic  acid. 

It  is  only  known  in  solution  and  in  the  state  of  vapour, 
since  it  polymerizes  at  the  ordinary  temperature  to  Tri-oxy- 
methylene  or  para-formic  aldehyde,  G^Ufi^,  a  white  crystalline 
mass  which  again  dissociates  upon  being  vaporized,  as  is  shown 
by  the  vapour  density  and  the  pungent  odour  evolved. 

Acetic  Aldehyde,  Aldehyde,  CHg—CHO,  was  formerly 
termed  "acetyl  hydride,"  CgHgO.H,  (Fourcroy  and  Fauquelin, 
1800;  composition  established  by  Liehig  in  1835;  name 
taken  from  alcohol  dehydrogenatum  ").  It  is  prepared  by 
passing  ammonia  gas  into  an  ethereal  solution  of  the  crude 
aldehyde,  obtained  by  oxidizing  alcohol  with  1^2^20^^  +  H2SO4 
and  drying  over  CaClg,  washing  the  precipitated  aldehyde- 
ammonia  with  ether,  and  finally  distilling  it  with  dilute 
sulphuric  acid.  It  is  obtained  in  large  quantity  as  a  bye- 
product  in  the  first  portions  of  the  distillate  in  the  manu- 
facture of  spirit.  For  its  production  in  place  of  vinyl  alcohol, 
C2H3.OH,  from  acetylene,  see  p.  54. 


136 


V.  ALDEHYDES  AND  KETONES. 


Colourless  mobile  liquid,  B.  Pt.  21°;  Sp.  Gr.  about  0-8. 
Has  a  peculiar  aromatic  and  suffocating  odour,  producing  a 
kind  of  cramp  in  the  chest  when  inhaled.  Burns  with  a 
luminous  flame  and  dissolves  sulphur,  phosphorus,  and  iodine. 
Chlorine  converts  it  into  acetyl  chloride,  and  carbonyl  chloride, 
COCI2,  into  a  liquid  of  fairly  constant  boiling  point,  formerly 
termed  "chloro-acetene." 

Para-aldehyde,  CqRj^^^.^,  is  a  liquid  difficultly  soluble  in 
water.  M.  Pt.  +  10° ;  B.  Pt.  124°,  i.e.  more  than  100°  above 
that  of  aldehyde.    Is  used  as  a  soporific. 

Meta-aldehyde,  (CgH^O)^,  crystallizes  in  white  prisms 
insoluble  in  water,  which  sublime  at  a  little  over  100°,  with 
partial  reconversion  into  aldehyde.    (See  B.  14,  2271). 

Meta-aldehyde  is  changed  back  again  into  ordinary  alde- 
hyde by  prolonged  heating  to  115°  in  sealed  tubes,  and  also, 
as  is  the  case  with  para-aldehyde,  by  distillation  with  some- 
what dilute  sulphuric  acid.  Para-aldehyde  reacts  in  the  same 
way  as  ordinary  aldehyde  with  PCI5,  but  not  with  NH3, 
NaHSOg,  AgNOg,  and  NH2OH.  The  constitution  of  para- 
aldehyde  may  be  taken  as  : 

0— CHv  •  CH3 
CHo .  CH<  >0     (Kekule  and  Zincke). 

\0— CH/CH3 

(The  connection  of  3  molecules  of  aldehyde  by  C-bonds 
cannot  be  assumed,  on  account  of  the  readiness  with  which 
para-aldehyde  breaks  up  into  the  former.) 

With  regard  to  these  and  other  polymeric  compounds,  the 
general  rule  has  been  proved  to  hold,  that  in  the  case  of  bodies 
of  similar  constitution,  the  one  of  simpler  composition  is  the 
more  soluble,  possesses  the  lower  melting  point,  and  is  the 
more  easily  vaporized. 

Acetal,  G^^^iOC^R^),.  B.  Pt.  104°.  Methylal,  CH2(OCH3)2. 
B.  Pt.  42°.  These,  especially  methylal,  are  frequently  used 
instead  of  aldehyde  for  the  carrying  out  of  condensation 
reactions,  (see  p.  134).  Methylal  is  employed  in  medicine  as 
a  soporific. 


CHLORAL. 


137 


Iso- valeric  aldehyde,  (Cll;Oj=C!H — CH^ — CHO,  from  iso-amyl 
alcohol.     B.  Pt.  92".     But  slightly  soluble  in  water. 

Normal  Heptylic  aldehyde,  Oevaniliol^  C7H14O,  is  obtained  by  the  dry 
distillation  of  castor  oil  under  diminished  pressure. 

Various  Aldehydes  C^.,  Cg,  Cy,  Cjo,  and  the  normal  Aldehydes  Cj^,  Cj4,  C^g, 
and  C18,  are  also  known,  the  latter  being  prepared  from  the  correspond- 
ing normal  acids. 

Mono-  and  Di-chlor-aldehyde,  CHgClCHO,  and  CHCI2CHO,  are 
liquids  boiling  respectively  at  85°  and  89°. 

Chloral,  CCI3.CHO,  (Liehig),  is  a  liquid  which  boils  at  98°, 
and  which — when  impure — easily  changes  into  a  solid  poly- 
meric modification,  meta-chloral,  but  is  regenerated  from  this 
upon  heating.  It  combines  readily  with  water  to  chloral 
hydrate,  CCl3.CH(OH)2,  (see  p.  131),  and  with  alcohol  to 
Chloral  alcoholate,  CCI3— CH(OH)(OC2H5),  and  Tri-chloro- 
acetal,  CCI3 — C}1{0. 02^1^)2-  The  end  product  of  the  action 
of  chlorine  upon  alcohol  consists  chiefly  of  the  last  three  sub- 
stances, which  are  converted  into  chloral  by  distilling  with 
sulphuric  acid,  and  rectifying  over  lime. 

Chloral  is  an  oily  liquid  of  a  sharp  and  characteristic  odour. 
It  combines  with  sodium  bisulphite,  ammonia,  hydrocyanic 
acid  and  acetic  anhydride,  and  reduces  an  ammoniacal  solution 
of  silver.  It  is  easily  oxidized  to  tri-chloracetic  acid,  and 
broken  up  by  alkali  into  chloroform  and  alkaline  formate  : 
CClgCH.O  +  HKO  =  CCl3H-fHC02K. 

Chloral  Hydrate,  CCl3.CH(OII)2,  forms  crystals  readily 
soluble  in  water,  melting  at  57°,  and  boiling  with  dissociation 
at  97°.  It  acts  as  a  soporific  and  antiseptic.  Sulphuric  acid 
converts  it  into  chloral. 


Of  the  aldehydes  poorer  in  hydrogen  must  be  mentioned,  in 
addition  to  Crotonic  aldehyde  (p.  134), 

Acrolein,  Acrylic  aldehyde,  Allyl  aldehyde,  CHg^CH— CHO, 
which  is  produced  by  the  oxidation  of  allyl  alcohol,  by  the 
distillation  of  fats,  and  by  heating  glycerine  with  bisulphato  of 
potash.  It  is  a  liquid  boihng  at  52°,  of  pungent  odour  (the 
smell  of  burning  fat  being  due  to  it),  and  of  violent  action 


138 


V.  ALDEHYDES  AND  KETONES. 


upon  the  mucous  membrane  of  the  eyes.  It  unites  in  itself 
the  properties  of  an  aldehyde  and  of  a  compound  poorer  in 
hydrogen. 

Acrolein-ammonia  yields  picoline,  CgH^N,  upon  distillation  (see 
pyridine  bases),  and  crotonic  aldehyde-ammonia,  by  an  analogous 
reaction,  collidine,  C8H;^iN. 

Acrolein  is  capable  of  combining  with  two  atoms  of  bromine  to 
Di-bromo-acrolein,  (di-bromo-propyl  aldehyde),  CHgBr — CHBr — CHO, 
a  compound  which  is  of  importance  in  the  synthesis  of  the  sugars.  (See 
p.  285.) 


B.  Ketones. 

The  lowest  member  of  the  series,  Acetone,  contains  three 
atoms  of  carbon.  The  higher  members,  from  solid. 
They  are  all  lighter  than  water,  e.g.^  the  Sp.  Gr.  of  acetone  is 
0-81  at  0°. 

Occurrence.  Acetone  is  present  in  urine,  methyl-nonyl 
ketone  in  oil  of  rue,  Euta  graveolens. 

For  constitution  and  nomenclature,  see  below. 

Modes  of  formation,  1.  By  the  oxidation  of  secondary 
alcohols,  which  lose  thereby  two  atoms  of  hydrogen  : 

CH3.CH(OH).CH3  +  0   =   CH3.CO.CH3  +  H2O. 

 Y  '  Y  ^ 

Iso-propyl  alcohol.  Acetone. 
Many  other  compounds  also,  which  contain  secondary  hydro- 
carbon radicles,  yield  ketones  upon  oxidation,  e.g.  iso-butyric 
acid. 

2.  From  acids  by  the  dry  distillation  of  their  calcium  or 
barium  salts,  carbon  dioxide  being  formed  : 

2CH3— COOca  =  qh'>^^  +  ^^3^^- 
When  two  different  acids  are  employed,  mixed  ketones,  i.e. 
ketones  containing  different  alcohol  radicles  result,  thus  r 

CH3— COOca  +  CH3.CH2. COOca   =  >C0  +  C03Ca. 

Calcium  acetate  and  propionate.         Methyl-ethyl- ketone. 


KETONES  ;  FORMATION  OF. 


139 


From  an  acid  C,,  there  is  thus  formed  a  ketone  C2i._i,  from 
two  acids  and  0,^  a  ketone  C„+ni-i-  When  formate  of 
calcium  is  used,  formic  aldehyde  results. 

3.  From  di-chlorides  containing  the  atomic  group  ^CClg  : 

(CH3)2CCl2  +  H^O  =  (CH3)2CO  Hr  2HC1. 
Acetone  chloride.  Acetone. 
One  might  expect  here  that  two  chlorine  atoms  would  be 
exchanged  for  two  hydroxyls,  and  a  compound  of  alcoholic 
character,  a  diatomic  alcohol,  acetonyl-glycol,  (CH3)2C=(OH)2, 
would  be  formed.  But  the  law,  already  mentioned  under 
aldehyde,  that  several  hydroxyls  cannot  as  a  rule  exist 
beside  one  another  joined  to  the  same  carbon  atom,  is  further 
exemplified  in  this  instance  also.  Derivatives  of  such  a 
glycol  are,  however,  capable  of  existence. 

4.  By  the  action  of  zinc-alkyl  upon  an  acid  chloride,  e.g, 
acetyl  chloride,  CH3.COCI: 

CH3.COCI  +  CHgZn  =  ch'>^^  (^^  =  iZn-) 

An  addition  compound  is  first  formed^  which  must  be 
quickly  decomposed  by  water,  otherwise  tertiary  alcohols  are 
produced.  This  method  of  formation,  which  was  devised  by 
Freund  in  1861,  allows  of  the  preparation  of  any  possible 
ketone  by  using  the  corresponding  zinc-alkyl  and  acid  chloride, 
e.g.: 

C3H7.CO.CI  +  C2H5zn  =  C3H7.CO.C2H5  +  Clzn. 

 ^  Y-  ' 

Butyric  chloride.  Ethyl-propyl  ketone. 

At  the  same  time  it  elucidates,  together  with  method  2,  the 
constitution  of  the  ketones,  from  the  constitution  of  the  corre- 
sponding acids.  Theoretically,  therefore,  ketones  are  com- 
pounds which  contain  the  carbonyl  group,  CO,  linked  on  both 
sides  with  an  alcohol  radicle,  R— CO — R.  If  the  alcohol 
radicles  are  the  same,  simple''  ketones  result,  and  if  diff'erent, 
mixed  "  ketones. 

The  ketones  may  also  be  regarded  as  derived  from  monobasic  acids 
by  the  exchange  of  their  hydroxyl  for  alkyl,  corresponding  with  modes 
of  formation  2  and  4,  and  also  from  aldehydes  by  exchange  of  hydrogen 
for  alkyl. 


140 


V.  ALDEHYDES  AND  KETONES. 


The  existence  of  ketones  with  less  than  3  atoms  of  carbon  is 
theoretically  impossible. 

5.  From  the  ketonic  acids  or  their  ethers,  e.g,  aceto-acetic 
ether,  CH3 — CO — CH2 — CO.OCgH^,  by  warming  with  moder- 
ately dilute  sulphuric  acid  or  with  dilute  alkalies.  This  im- 
portant reaction  will  be  treated  of  at  greater  length  under 
aceto-acetic  ether. 

6.  From  the  hydrocarbons  of  the  acetylene  series  (see  p.  54),  by  the 
action  of  mercuric  salts  and  also  of  dilute  sulphuric  acid. 

Isomers.  The  ketones  show  among  themselves  the  same 
isomerism  as  the  secondary  alcohols.  This  isomerism  depends 
on  the  one  hand  upon  the  isomerism  of  the  alcohol  radicles 
which  are  linked  together  by  the  CO-group,  (different  carbon 
atom  chains),  and  on  the  other  by  the  position  of  the  oxygen 
atom  on  similar  carbon  chains,  (isomerism  of  position) ;  thus, 
C^H^— CO— CH3  is  isomeric  with  C3H7— CO— C2H5. 

The  aldehydes  containing  an  equal  number  of  carbon  atoms 
in  the  molecule  are  always  isomeric  with  the  ketones,  since 
both  classes  of  compounds  are  formed  from  isomeric  alcohols 
by  the  separation  of 

This  kind  of  isomerism  may  also  be  compared  with  metamerism,  e.g. 
with  that  of  methyl-butyl  ether  and  ethyl-propyl  ether. 

Nomenclature.  After  the  name  of  the  alcohol  radicle  the 
syllable  "ketone"  is  appended,  e,g.  di-ethyl  ketone,  {G^^\QO, 
and  methyl-ethyl  ketone,  CH3 — CO — CgH^.  Acetone  is  con- 
sequently di-methyl  ketone.  The  names  of  the  simple  ketones 
are  also  derived  from  the  acids  which  yield  them,  e.g. 
"  Valerone,"  (0^119)200,  from  valeric  acid. 

Baeyer  (B.  19,  160)  terms  the  ketones  keto-substitutmi  products  of 
the  hydrocarbons,  and  betokens  the  position  of  the  oxygen  similarly  to 
that  of  the  hydroxyl  in  the  oxy-acids  or  of  the  halogen  in  the  substituted 
fatty  acids,  by  marking  the  end  carbon  atom  with  w,  and  the  following 

ones  in  their  order  with  a,  j8,   /3',  a'.    In  this  way  acetone  is 

termed  keto-propane,  and  ethyl-methyl  ketone  a-keto-butane,  etc. 

Behaviour.  1,  The  ketones  are  reducible  to  secondary 
alcohols  : 

(GR,),CO  +  R,  =  (OH3)2CH.OH. 


KETONES  ;  BEHAVIOUR  OF. 


141 


At  the  same  time  pinacones  are  formed  in  small  quantity,  (see 
p.  191),  these  going  into  the  pinacolines  (pp.  77  and  144)  correspoii<ling  to 
the  ketones,  when  warmed  with  acids. 

2.  Oxidizing  agents,  e  g.  ^^Gr^f)^  and  dilute  HgSO^,  slowly 
convert  the  ketones  into  acids  containing  a  lesser  number  of 
carbon  atoms  in  the  molecule,  (not — as  in  the  case  of  the 
aldehydes — into  acids  containing  an  equal  number),  the  carbon 
chain  being  broken : 

CH3— CO.CH3  +  O3   -  CH3.COOH  +  CO2  +  H2O. 

Since  carbon  is  tetravalent,  the  CO  group  in  the  ketone,  being 
already  linked  to  two  alcohol  radicles,  can  only  go  over  into  the  group 
COOH,  which  characterizes  the  acids  (p.  152),  if  one  of  the  alcohol 
radicles  be  split  off.  Should  the  alcohol  radicles  which  are  joined  to 
the  carbonyl  be  of  an  unequal  size,  it  is  the  larger  one  which  is  as  a 
rule  separated  by  the  oxidation,  and  then  further  oxidized  by  itself. 
{Popoff's  law  ;  see  B.  15,  1194  ;  17,  Ref.  315). 

Since  the  acids  formed  by  oxidation  bear  no  reciprocal  relation  to  the 
ketone,  and  the  oxidation  process  is  more  complicated  than  in  the  case 
of  the  aldehydes,  it  is  easy  to  understand  w^hy  the  ketones  do  not 
possess  reducing  properties. 

3.  Phosphorus  pentachloride,  PCI5,  converts  the  ketones 
into  the  corresponding  dichlorides,  acetone,  for  instance,  into 
acetone  chloride,  (CH3)2CCl2. 

4.  Addition-reactions.  (a)  The  ketones  do  not  as  a  rule 
combine  with  water  and  alcohol,  for  the  reasons  given  under 
the  aldehydes  and  at  p.  139. 

They  form  with  mercaptan  mercaptols,"  analogous  to  acetal,  e.g, 
{Cll,),C{SC,Ji,),,    (B.  18,  883.) 

(b)  With  ammonia  there  result  the  (basic)  acetone-amines, 
with  separation  of  water,  e.g.  di-acetone-amine,  CgHj3N0,  tri- 
acetone-amine,  CgH^^NO,  (Heintz) ;  this  reaction  is  more 
complicated  than  that  with  the  aldehydes,  two  or  three 
molecules  of  acetone  combining  with  one  molecule  of  ammonia, 
with  elimination  of  water. 

(c)  Tlie  ketones  which  contain  the  group  CH3 — CO — ,  and 
also  some  others,  combine  with  acid  sodium  sulphite  to  crystal- 

OH 

line  compounds,  e.g.  acetone  to  (CH3)2  C<^gQ  +  HgO, 
(glancing  mother-of-pearl  plates) ;  these  go  back  into  ketones, 


142 


V.  ALDEHYDES  AND  KETONES. 


for  the  most  part,  when  treated  with  soda  solution.  This 
very  important  reaction  is  made  use  of  in  separating  and 
purifying  the  ketones. 

((/)  With  hydrocyanic  acid  are  formed  the  nitriles  of  higher 
acids,  as  in  the  case  of  the  aldehydes. 

5.  The  ketones,  unlike  the  aldehydes,  do  not  possess  the 
property  of  polymerizing,  but  they  form  condensation  products. 
Just  as  aldehyde  is  converted  into  crotonic  aldehyde,  so  is 
acetone,  by  the  action  of  many  reagents — e.g,  CaO,  KOH,  HCl, 
and  H2SO4 — converted  with  elimination  of  water,  into  mesityl 
oxide,  CgH^^O,  phorone,  CgH^^O,  or  mesitylene,  CgH^g?  accord- 
ing to  the  conditions,  (see  benzene  derivatives) : 

2C3HeO  =  CgH.oO  +  H2O. 

SCgHgO  =  +  2H2O. 

SCgHgO  =  CqH^2    +  3H2O. 
Analogous  condensations  also  ensue  with  other  ketones  or 
aldehydes  under  the  influence  of  dilute  caustic  soda  or  of 
sodium  ethylate,  (B.  20,  655).    In  this  way  the  more  compli- 
cated ketones  result,  (A.  218,  121). 

6.  Sulphuretted  hydrogen  converts  the  ketones  into  thio- compounds, 
e.g.  acetone  into  thio-acetone,  CH3 — CS — CH3,  (B.  16,  1368). 

7.  Halogens  give  rise  to  substitution  products. 

8.  Like  the  aldehydes,  the  ketones^ — even  C35 — combine 
with  hydroxylamine  to  oximes,  e.g.  acetoxime.  {V,  Meyer ^ 
B.  15,  1324,  2778;  16,  823,  1784,  etc.)    Thus  : 

(CH3)2CO  +  NH2OH  =  H2O  +  (CH3)2C^N.OH. 

Acetoxime. 

These  are  for  the  most  part  solid,  readily  volatile  compounds 
which  decompose  backwards  upon  heating  with  hydrochloric 
acid.  Their  hydroxyl  is  replaceable  by  alkyls  or  by  acid 
radicles,  the  alkyl  compounds  being  broken  up  by  HCl  into 
the  ketone  and  alkylated  hydroxylamine,  NH2 .  OR.  From 
this  reaction  we  arrive  at  the  constitution  of  the  oximes,  i.e. 
the  OH  in  them  is  bound  to  N.  By  the  reduction  of  the  oximes 
primary  amines  are  formed,  as  in  the  case  of  the  aldoximes 
(p.  134). 


ACETONE. 


143 


9.  Analogous  reactions  follow  with  the  hydrazines,  e.g. 
phenyl  hydrazine,  C^H^— NH-NHg,  {E.  Fischer,  B.  17,  572), 
with  the  formation  of  "  hydrazones;"  (pp.  135  and  373). 

(CH3),C0  4-H,N-NH-CeH, 

=  (CH3),C^N-NH-C,H,  +  H,0. 
V  .  ' 

Acetone-phenyl-hydrazone. 

Both  reagents  are  therefore  of  great  value  for  the  recog- 
nition of  the  aldehydic  or  ketonic  character  of  a  substance. 

10.  Nitrous  acid  (nitrous  ether  and  sodium  ethylate)  gives  rise  to  Iso- 
nitroso-ketones,  e.g.  iso-nitroso-acetone,  CHg — CO— CH=N.OH,  by 
the  separation  of  HgO  and  the  replacement  of  H2  by  the  group 
^N.OH  (oxime).  These  are  converted  by  reduction  into  Amido- 
ketones,  e.g.  amido-acetone,  CH3 — CO — CH2.NH2,  unstable  basic  com- 
pounds which  readily  give  up  water  and  change  into  aldines  (p.  491). 
The  oxime  group  in  the  iso-nitroso-ketones  can  be  replaced  by  an  atom 
of  oxygen,  whereby  ketone-aldehydes  or  di-ketones  (p.  221)  are  pro- 
duced. 

Acetone,  CgHgO,  =  CH3— CO— CH3. 

Acetone  has  been  known  for  a  long  time ;  its  formula  was 
established  by  Liehig  and  Dumas  in  1832. 

It  is  present  in  very  small  quantity  in  normal  urine,  in  the 
blood,  in  serum,  etc.,  but  in  much  larger  quantity  in  patho- 
logical cases  such  as  acetonuria  and  diabetes  mellitus.  It 
is  produced,  among  other  ways,  by  the  distillation  of  sugar, 
gum,  cellulose,  etc.,  and  is  therefore  present  in  wood  spirit; 
also  by  acting  upon  allylene,  C3H4,  with  HgCl2  (p.  54).  On 
the  large  scale  it  is  prepared  by  the  dry  distillation  of  acetate 
of  lime. 

Properties.  (See  above,  under  general  behaviour  of  the 
ketones.)  Liquid  of  peculiar  ethereal  and  refreshing  odour, 
B.  Pt.  56°.  Soluble  in  water,  and  separated  from  the  aqueous 
solution  on  addition  of  salts.  Miscible  also  with  alcohol  and 
ether.  KMnO^  does  not  oxidize  it  in  the  cold,  but  CrOg  does, 
with  formation  of  acetic  and  carbonic  acids.  Shows  the 
aldehydic  reaction  with  fuchsine  and  sulphurous  acid. 

Iso-nitroso-acetone,  CH3— CO— CH=N.OH  (B.  15,3067),  is  formed 
by  the  action  of  nitrous  acid  upon  acetone. 


L44 


V.  ALDEHYDES  AND  KETONES. 


Detection  of  acetone,  e.g.  by  conversion  into  indigo  by  means  of 
o-nitro-benz-aldehyde. 

Chloro -acetone,  metacyl  chloride^  CHg  —CO — CHgCl,  is  a  liquid  which 
produces  a  copious  flow  of  tears.    B.  Pt.  119°. 

Per-bromo -acetone,  CBrg— CO— CBrg,  is  also  known.    (See  p.  322.) 

Mesityl  oxide,  CgHjoO,  =  CH3— CO— CH=C(CH3),,  {Kane,  1838, 
Bacyer),  is  a  liquid  of  aromatic  odour,  boiling  at  132°. 

Phorone,  C9H14O,  =  CH3— CO— CH-C(CH3)[CH=C(CH3)2],  forms 
yellow  crystals  which  melt  easily.  Both  of  these  compounds  are  ob- 
tained by  saturating  acetone  with  hydrochloric  acid  gas  (A.  180,  1). 

Acetoxime,  (CH3)2C=N — OH.  Crystals,  melting  at  60°  and  volatiliz- 
ing at  135°  without  decomposition,  readily  soluble  in  water,  alcohol 
and  ether. 

Di-ethyl  ketone,  propione,  (02115)200.    M.  Pt.  104°. 

Di-propyl  ketone,  butyrone,  (03H7)20O.    M.  Pt.  144°. 

Pinacoline,  methyl-tertiary-hutyl-ketone,  OH3 — 00 — C=(OH3)3, 
results  from  the  action  of  dilute  sulphuric  acid  upon  pinacone. 
(See  p.  191.) 

Methyl-n-  nonyl  ketone,  OH3 — 00 — OgH^g,  is  the  chief 
constituent  of  oil  of  rue  (from  Euta  graveolens).  M.  Pt. 
225°.  Ketones  with  11,  12,  13,  14,  15,  16,  17,  18,  and  19 
carbon  atoms  are  also  known ;  further,  Laurone,  023X14^0,  from 
calcium  laurate ;  My ri stone,  O27H54O,  from  calcium  myristate; 
Palmitone,  G^^^^^O^  from  calcium  palmitate;  Stearone, 
C35H7QO,  from  calcium  stearate ;  and,  finally,  the  ketones,  O20, 
O22  and  O24,  which  are  obtained  by  distilling  the  normal  hepty- 
late  with  myristate,  palmitate,  or  stearate  of  lime.  All  these 
ketones  have  been  converted  by  Krafft  into  the  corresponding 
paraffins,  by  first  transforming  them  into  the  chlorides, 
C^HguOla,  by  means  of  POI5,  and  then  heating  the  latter  with 
hydriodic  acid  and  phosphorus.  The  proof  of  the  normal 
character  of  these  various  compounds  is  given  by  the  suc- 
cessive transformation  in  a  descending  scale  of  the  higher 
molecular  acids  0^,  into  acids  On_i,  (by  distilling  their  barium 
salts  with  barium  acetate  and  oxidizing  the  ketones  O^.j  so 
produced  to  acids  On_i),  conversion  of  each  acid  and  each  ketone 
into  the  corresponding  paraffins,  and  comparison  of  these  last. 

[Continued  on  page  146. 


V.  ALDEHYDES  AND  KETONES.  145 
COMPARISON  OF  THE  ALDEHYDES  AND  KETONES. 


Aldehydes,  X.CHO. 


Ketones,  ^CO. 


Modes  of  formation. 

1.  By  the  oxidation  of  primary 

alcohols,  Cn*  (and  other  sub- 
stances). 

2.  By  the  reduction  of  acids,  Cn. 

(Distillation  of  the  Ca  salts 
with  calcium  formate). 

3.  From  the  di-chlorides,X.  CHClg. 


Properties. 

1.  Reducible  to  primary  alcohols. 

2.  Oxidizable  to  acids,  Cn;  strongly 

reducing. 

3.  Yield  with  PCI5  di-chlorides, 

— CHCI2. 

4.  Capable  of  combining  with  [{a) 

water  ;  (6)  alcohol,  acetic  acid 
(seldom)];  (c)  ammouia;  [d) 
sodium  bisulphite,  to  crystal- 
line compounds ;  (e)  hydro- 
cyanic acid,  to  nitriles  of 
higher  acids. 

5.  Capableof  polymerization,  often 

with  production  of  resin  when 
KOH  is  used. 

6.  Condensible,    e.g.     to  aldol, 

C4H8O2,  and  to  crotonic  alde- 
hyde. 

7.  Capable  of  substitution,  e.g.  to 

chloral,  CCI3 .  CHO. 


8.  Yield  with  HgS,  thio-aldehydes. 

9.  Yield     with  hydroxylamino, 

oximes,  — CH=N  .  OH. 


Modes  of  formation. 

By  the  oxidation  of  secondary 
alcohols,  Cn  (and  other  com- 
pounds). 

From  acids  by  distillation  of 
their  mixed  calcium  salts. 


3.  From  di-chlorides,  X>CCl2. 

4.  From  acid  chlorides  and  zinc 

alkyl. 

5.  From  ketonic  acids,  with  separ- 

ation of  COg. 

Properties. 

1 .  Reducible  to  secondary  alcohols. 

2.  Oxidizable  to  acids,  Cn-x;  uot 

reducing. 

3.  Yield  with  PCI5  dichlorides, 

>0Cl2. 

4.  Capable  of  combining  with  [{a) 

water;  (6)  alcohol,  both  sel- 
dom], (c)  ammonia,  toacetone- 
amines  with  separation  of 
water;  {d)  sodium  bisulphite, 
to  crystalline  compounds  ;  (e) 
hydrocyanic  acid,  to  nitriles 
of  higher  acids. 


Condensible,  e.g. 
C9H14O,  C9H12. 


to  CeHioO, 


to 


Capable  of  substitution,  e.g, 

chloro-acetone, 

CH3— CO-CH2CI. 
Yield  with  H2S,  thio-acetones. 
Yield     with    hydroxy!  amine. 

oximes,  >C  =  N  .  OH. 


(606) 


n  means  an  equal  number  of  carbon  atoius. 


146 


VI.  MONOBASIC  FATTY  ACIDS. 


We  have,  for  instance,  the  following  relations  : 

Paraffins.  Ketones.  Acids. 

  CjiHooO 

Cn^2,£  .»»»;;;;::^CnH2A  ' 

CioHoaO-^^  ""Z.^^  1 


If,  for  example,  the  acid  C12II24O2  is  normal,  so  is  the  paraffin  C12H26, 
and  also  the  ketone  C13H26O,  since  the  preparation  of  the  last  depends 
upon  the  exchange  of  the  OH  of  the  acid  for  CH3,  the  new  C  atom  being 
again  an  end  one.  Consequently  the  paraffin  C13H28  is  also  normal  and, 
if  this  be  identical  with  the  paraffin  C13H28  from  the  acid  C13H26O2,  the 
latter  must  likewise  be  normal.  Since,  further,  the  acid  G11H22O2  re- 
sults from  the  oxidation  of  the  ketone,  C13H26O  or  Ci^Hig — CO — CH3,  it 
must  be  normal,  and  therefore  also  the  paraffin  C11H24.  The  paraffins 
Cii,  C12,  and  Ci3  are  thus  to  be  referred  to  one  another  through  the  acid 
Ci2H2402>  hydrocarbons  C13,  C14,  and  C^g  through  the  acid  C14,  and  so 
on;  likewise  the  acids  Cg,  Cjo,  and  C^  through  the  paraffin  C^,  etc., 
etc.  Now  the  acids  C125  ^u,  C^g,  and  C^g,  which  occur  in  nature,  yield 
as  a  matter  of  fact  ketones,  paraffins,  and  acids  which — from  their  syn- 
theses— are  undoubtedly  derived  from  nonylic  acid  ;  consequently  they 
themselves  and  all  their  derivatives  are  normal.  (Cf.  the  Aldehydes  and 
ketones,  table,  p.  145.) 


VI.  MONOBASIC  PATTY  ACIDS. 

A.  Saturated  Acids,  C^HgA.    (See  Table,  p.  147.) 

By  the  oxidation  of  the  primary  alcohols  or  of  their  corre- 
sponding aldehydes  the  monobasic  fatty  acids  are  formed,  the 
saturated  alcohols  yielding  the  saturated  monobasic  fatty 
acids,  or  "  acids  of  the  aliphatic  series  "  as  they  are  termed, 
corresponding  to  which,  as  to  the  alcohols,  there  are  unsaturated 
compounds.  These  acids  are  monobasic,  i.e.  contain  in  the 
molecule  only  one  replaceable  atom  of  hydrogen,  because  they 
give  rise  to  only  one  series  of  salts  or  of  ethers.  They  are 
known  as  the  fatty  acids,  on  account  of  many  of  them  being 
either  contained  in  fats  or  resulting  from  these  by  oxidation. 

The  lower  members  of  the  series  are  liquids  of  pungent 
odour  and  corrosive  action  which  boil  without  decomposition, 


VI.  MONOBASIC  FATTY  ACIDS. 


147 


oooooooooooooo^ 

(MT)1C000O<M^«5tX3O-t<Q0-^O!M 

OOOOOOOOQOOUOOQ 
■^1  _  „ 


O  M-j 


0)  o 


lO    TiH    CO         Ci  ,(M 
O    (^^    CO    lO  CO  o 
(M    (M    C<l  (M  lo^ 


^    ^lij    CO  riiJ 


>   >  ^ 


O  O  O 


o 

o 


o  o  o  o  ^ 

(M        Tf        CO  00 

^ 

«5         1>        00         C35  rH 

o  o  o  o  o 


1=1  ? 


.2  o 


O  H 


p 


^  ^  rH 


C     W     O  ^ 


148 


VI.  MONOBASIC  FATTY  ACIDS. 


dissolve  readily  in  water,  and  show  a  strongly  acid  reaction. 
The  middle  members  have  an  unpleasant  smell  like  that  of 
rancid  butter  or  perspiration,  and  are  oily  and  but  slightly 
soluble  in  water.  Mobility,  odour  and  solubility  diminish 
with  increasing  carbon.  The  higher  members,  from  C^q  on,  are 
solid,  like  paraffin,  and  insoluble  in  water,  and  can  only  be 
distilled  without  decomposition  in  a  vacuum.  Their  acid 
character  no  longer  finds  expression  in  their  reaction,  but  in 
their  capability  of  forming  salts  with  bases.  They  remain 
easily  soluble  in  alcohol  and  especially  in  ether. 

For  the  laws  governing  the  melting  and  boiling  points,  see  pp.  28  and 
26.  The  Sp.  Gr.  of  the  liquid  acids  is  at  first  >  1,  and  from  C3  onwards 
<  1,  and  it  decreases  continuously  down  to  about  0*8,  the  paraffin 
character  of  the  hydrocarbon  radicle  becoming  preponderant. 

Occurrence.  Many  of  the  acids  of  this  series  are  found  in 
nature  in  the  free  state,  but  more  frequently  as  ethers,  viz.  : — 
{a)  ethers  of  monatomic  alcohols  (see  wax  varieties),  (6)  ethers 
of  glycerine  or  glycerides,  in  most  of  the  vegetable  and  animal 
fats  and  oils.    For  further  particulars  see  p.  161. 

Formation.  1.  By  the  oxidation  of  the  primary  alcohols, 
CuHgn+iOH,  or  their  aldehydes,  Ci^HguO,  by  means  of  K2Cr207 
or  MnOg  and  dilute  H2SO4,  or  by  the  oxygen  of  the  air  in 
presence  of  platinum  or  of  nitrogenous  substances,  e.g.  acetic 
acid  from  alcohol. 

1^.  Acids  containing  less  carbon  are  formed  by  the  oxidation  of  many 
other  compounds,  such  as  ketones,  secondary  and  tertiary  alcohols, 
etc. ,  with  separation  of  carbon.  The  higher  molecular  acids  of  this  series 
are  likewise  converted  into  their  lower  homologues  upon  oxidation. 

2.  Several  acids  have  been  prepared  from  the  halogen  com- 
pounds CnHgn-iXg,  which  contain  the  group  — CX3,  e.g. : 
HCCI3  +  4K0H  -  H.CO2K  +  3KC1  +  2H2O. 

From  this  mode  of  preparation  one  might  expect  an  exchange 
of  the  three  chlorine  atoms  for  three  hydroxyls,  with  formation 
of  the  intermediate  compounds  H  .  C=(0H)3  or  E — C(0H)3. 
Such  compounds  are  however  incapable  of  existence  for  the 
reasons  stated  under  the  aldehydes  and  ketones,  going  over 
into  acids  with  elimination  of  water,  thus  : 

E— C(0H)3    -    R— CO.OH  +  H2O. 


MODES  OF  INFORMATION. 


149 


But  derivatives  of  these  (whicli  may  be  regarded  as  triatoniic 
alcohols  and  termed  "ortho-acids,")  are  known,  e.g.  ortho-formic 
ethyl  ether,  HC(OC2H5)3,  a  neutral  liquid  of  aromatic  odour,  insoluble 
in  water,  and  boiling  at  146°. 

3.  From  the  cyanogen  compounds  of  the  alcohol  radicles, 
Cj^Hgn+iCN.  The  cyanides,  i.e.  nitriles,  which  are  prepared  by 
warming  the  iodides  of  the  alcohol  radicles  with  cyanide  of 
potassium,  are  converted  into  the  fatty  acids  and  ammonia  by 
saponification,  e.g.  by  heating  with  potash,  with  dilute  or 
concentrated  hydrochloric  acid,  or  with  sulphuric  acid  diluted 
with  its  own  volume  of  water,  thus  : 

CH3.CN  +  2H2O  =  CH3.CO2H  +  NH3. 

In  this  way  hydrocyanic  acid  yields  formic  acid  and 
ammonia,  and  it  may  therefore  be  regarded  as  the  nitrile  of 
the  former.  Amides  are  formed  as  intermediate  products. 
(See  pp.  107  and  180.) 

The  great  importance  of  this  reaction,  by  means  of  which 
we  can  obtain  an  acid  Cn+i  from  an  alcohol  C^,  has  been 
alread}^  indicated,  (p.  108).  And  since  the  acids,  albeit  with 
some  difficulty,  can  be  converted  by  reduction  into  the  corre- 
sponding alcohols,  it  is  thus  possible  to  build  up  synthetically, 
step  by  step,  the  alcohols  richer  in  carbon  from  those  poorer 
in  carbon,  a  circumstance  which  is  of  especial  importance 
in  the  case  of  the  normal  alcohols.    {Lieben  and  Ross%  see 

p.  77.) 

4.  The  acids  may  be  regarded  as  resulting  from  the  paraffins 
Cn-iH2(n— 1)+2  and  CO2,  e.g.  acetic  acid  from  CH4  and  CO2,  and  formic 
acid  from  Hg  and  CO2.  These  two  components  can  in  fact  be  made  to 
combine  indirectly,  thus  carbonic  acid  unites  with  potassium  or  sodium 
alkyl  upon  warming,  (  WanMyn)  : 

CHgNa  +  CO2  =  CHg.CO^Na. 

Formic  acid  is  obtained  in  an  analogous  manner  from  nascent 
hydrogen  and  carbon  dioxide,  under  the  influence  of  the  electric  dis- 
charge : 

H2  +  CO2  =  H.CO2H; 

or  from  hydrogen,  potassium  and  carbon  dioxide,  when  the  potassium 
is  placed  in  a  bell  jar  filled  with  moist  carbonic  acid,  (Kolbe  and  Schmitt^ 
1861). 


150 


VI.  MONOBASIC  FATTY  ACIDS. 


5.  By  passing  carbonic  oxide  over  heated  caustic  alkali  or  alcoholate, 
thus  : 

CHg.ONa  +  CO  =  CHg.COoNa  (at  160°). 
H.ONa  +  CO  =  H.CO^Na. 

6.  Acid  chlorides  (p.  176)  are  produced  by  the  action  of 
phosgene,  COCI2,  upon  zinc  alkyl  : 

COCI2  +  znCHg  =   CH3.COCI  +  znCl; 

Acetyl  chloride. 

and,  on  decomposing  these  with  water,  the  acids  themselves 
are  obtained  : 

CH3.CO.CI  +  Hp  =   CH3.CO.OH  +  HCl. 

7.  From  acids  poorer  in  hydrogen  by  direct  or  indirect  addition  of 
the  latter,  e.g.  propionic  acid,  CgHgOg,  from  acrylic  acid,  C3H4O2.  This 
addition  of  hydrogen  may  be  effected  directly  by  hydrioclic  acid  and 
phosphorus,  or  indirectly,  for  instance,  by  addition  of  hydrobromic 
acid  and  backward  substitution.  Unsaturated  acids  also  yield  saturated 
ones  containing  fewer  carbon  atoms  when  fused  with  potash,  e.g.  1  mol. 
crotonic  acid,  C4Hg02,  yields  2  mols.  acetic  acid,  C2H4O2. 

8.  From  the  oxy-acids,  also  termed  alcoholic  acids,  by 
'heating  them  with  hydriodic  acid  : 

C3Hg03  +  2HI  =  CgHgOg  +  I2  +  H2O. 

Lactic  acid.  Propionic  acid. 

9.  From  many  polybasic  acids,  by  the  partial  separation  of 
CO2,  thus  : 

C2O4H2  =  CO2  +  H.CO2H. 
Oxalic  acid.  Formic  acid. 

10.  Aceto-acetic  ether  syntheses.    The  homologues 

K_CH2— COOH  and  ^,>CH— COOH 

can  be  prepared  from  acetic  acid  by  first  converting  the  latter 
into  aceto-acetic  ether,  CH3 — CO — CH2 — COO.CgHg,  intro- 
ducing the  alcohol  radicle  into  this,  and  then  breaking  up 
backwards  the  compound  so  obtained  by  concentrated  alcoholic 
potash.  This  reaction  will  be  gone  into  more  fully  under 
aceto-acetic  ether  (p.  226). 

10a.  An  analogous  reaction  follows  on  the  use  of  malonic  ether 
(seep.  234). 


BEHAVIOXTR. 


151 


Separation.  Natural  fats  are  nearly  all  glycerides  of  several  acids,  so 
that  a  mixture  of  acids  results  on  their  saponification.  This  mixture 
may  be  separated  into  its  components  as  follows  : 

{a)  By  fractional  distillation  in  a  good  vacuum  ;  [h)  by  fractional  pre- 
cipitation of  an  alcoholic  solution  of  the  acids  by  means  of  magnesium 
acetate,  calcium  chloride,  etc.,  the  acids  richer  in  carbon  being  pre- 
cipitated first;  (c)  by  fractional  solution  :  the  dry  barium  salts  of  formic, 
acetic,  propionic  and  butyric  acids  are  very  differently  soluble  in  alcohol, 
the  solubility  increasing  rapidly  w^ith  increasing  carbon  ;  [d)  by  frac- 
tional saturation,  and  distillation  of  the  non-combined  acid. 

Behaviour,  1.  Salts.  The  foregoing  acids  being  monobasic, 
they  form  neutral  salts,  e.g.  (C2H302)Na.  But  they  also  yield 
acid  salts — the  so-called  super-acid  salts — from  the  existence  of  which 
one  might  feel  inclined  to  doubt  their  monobasic  nature.  These  salts 
are,  however,  only  crystallizable  from  a  strongly  acid  solution,  break 
up  on  addition  of  water,  and  also  lose  their  excess  of  acid  upon  heating. 
It  is  therefore  permissible  to  regard  them  as  molecular  compounds  of  the 
neutral  salts  with  the  acids,  in  which  the  latter  play  the  r61e  of  water 
of  crystallization.  All  the  other  chemical  characteristics  of  the  acids 
go  to  prove  their  monobasicity. 

2.  Besides  salts,  the  monobasic  acids,  simple  or  substituted, 
yield  other  derivatives  in  a  manner  exactly  analogous  to  that 
of  the  monatomic  alcohols.  The  typical  hydrogen  atom  is 
replaceable  by  an  alcohol  radicle  with  formation  of  a  compound 
ether,  or  by  a  second  acid  radicle  with  formation  of  an  an- 
hydride; the  hydroxy  1  may  further  be  replaced  by  halogen, 
especially  chlorine,  to  an  acid  chloride  or  chloro-anhydride,  by 
8H  to  a  thio-acid,  by  NHg  to  an  amide,  etc.  (See  Acid 
derivatives,  p.  173.) 

3.  Halogens  act  upon  the  acids  as  substituents  (see  p.  168). 

4.  Upon  heating  with  soda-lime,  carbonic  acid  is  separated 
{uid  a  paraffin  formed,  see  e.g.  methane.  Paraffins  also  result 
from  the  electrolysis  of  the  alkaline  salts  of  the  acids,  (see 
ethane). 

5.  Most  of  the  acids  are  relatively  stable  towards  oxidizing 
agents,  formic  acid  alone  being  readily  oxidized  to  carbonic 
acid,  and  being  therefore  a  reducing  agent. 

6.  When  the  lime  salts  of  the  acids  are  heated  with  calcium 
formate,  they  are  reduced  to  aldehydes,  and  when  heated  for 


152 


VI.  MONOBASIC  FATTY  ACIDS. 


a  lengthened  period  with  hydriodic  acid  and  phospliorus,  to 
paraffins. 

7.  For  their  transformation  into  the  amine  bases,  G^_i^  see 
p.  182. 

8.  For  the  building  up  of  the  higher  acids,  see  pp.  145  and 


Constitution,  It  follows  from  their  modes  of  formation, 
especially  3,  4,  and  6,  and  also  from  their  behaviour  (see  3 
above),  that  acetic  acid  and  its  higher  homologues  contain 
alcohol  radicles.  The  conversion  of  the  alcohols  into  acids 
containing  one  atom  of  carbon  more,  by  means  of  the  cyanides, 
is  especially  strong  proof  of  this.  The  latter  contain  the 
alcoholic  radicle  bound  to  the  cyanogen  group  — C=N,  and 
when  they  are  saponified  the  alcohol  radicle  remains  un- 
changed, and  the  trivalent  nitrogen  is  replaced  by  0"  and 
(OH)',  both  of  these  attaching  themselves  to  the  carbon  atom 
of  the  original  cyanogen,  and  so  forming  the  group 


Consequently  all  the  oxygen  in  the  acid  is  bound  to  a  singk 
carbon  atom  in  the  form  of  the  group  COgH.  This  group, 
which  is  termed  carboxyl,  is  characteristic  of  the  existence  of 
acid  properties.  The  monobasic  acids  may  therefore  be  re- 
garded as  compounds  of  the  alcohol  radicles  with  carboxyl, 
thus : 


Formic  acid  is,  in  this  way,  the  hydrogen  compound  of 
carboxyl,  H.COgH. 

The  acids  are  distinguished  as  primary,  secondary,  or  tertiary,  accord- 
ing as  the  alcohol  radicles  which  they  contain  are  primary,  etc. 

The  monobasic  acids  may  be  regarded  as  being  derived 
from  the  hypothetical  carbonic  acid,  C0(0H)2,  by  exchange  of 
hydroxyl  for  alkyl  or  hydrogen  : 

CO<^Q^^  =  Butyric  acid ;  C)0<^qjj  =  Formic  acid. 

They  are  also  termed  organic  carboxylic  acids,  and  may  also 


182. 


CONSTITUTION. 


153 


be  considered  as  derived  from  the  parallius  by  exchange  of  an 
atom  of  hydrogen  for  carboxyl.  Thus  acetic  acid  is  methane- 
carboxylic  acid,  etc. 

There  is  no  room  for  doubt  that  it  is  the  hydrogen  atom  of 
the  carboxyl  group,  the  so-called  typical "  hydrogen  atom, 
which  is  replaced  by  metals  in  the  formation  of  salts,  for  the 
foregoing  acids  are  all  monobasic,  and  consequently  the  number 
of  hydrogen  atoms  present  in  the  alcohol  radicle  is  of  no 
moment  for  the  acid  character.  In  the  di-  and  polybasic 
acids,  the  presence  of  two  or  more  carboxyls  must  therefore 
be  assumed. 

If  one  compares  the  composition  of  the  primary  alcohols,  R — CHg.OH, 
with  that  of  the  corresponding  acids,  R — CO. OH,  (R  =  alkyl  or  hydro- 
gen), the  latter  are  seen  to  be  derived  from  the  former  by  the  exchange 
of  two  atoms  of  hydrogen  of  the  carbinol  for  one  atom  of  oxygen.  The 
character  of  the  original  substance  is  thus  completely  changed  by  the 
entrance  of  the  electro-negative  (acidifying)  oxygen. 

It  must  not  be  forgotten  that  the  constitution  of  the  aldehydes  and 
ketones,  of  the  primary  and  secondary  alcohols,  of  glycol,  ethylene, 
ethylene  bromide,  etc.,  are  deduced  from  the  constitution  of  the  acids. 

The  rational  formulae  of  the  foregoing  acids  may  be  written  in 
various  ways,  according  to  the  reaction  which  it  is  desired  to  indicate. 
(Cf.  p.  19.) 

The  group  G^Rfi —  or  CH3.CO — ,  acetyl,  which  together 
with  hydroxyl  is  common  to  most  of  the  acetic  acid  deriva- 
tives, and  which  can  be  transferred  like  an  element  to  other 
compounds  by  exchange,  is  termed  the  radicle  of  acetic  acid 
(see  p.  22).  The  radicles  of  the  homologues  are  similarly 
compounded,  e.g.  H.CO — ,  formyl ;  C3H5O — ,  propionyl; 
C^HyO,  butyryl,  etc. 

The  aldehydes  may  be  looked  upon  as  hydrogen  compounds  of  the  acid 
radicles,  and  the  ketones  as  compounds  of  the  latter  with  alcohol 
radicles,  thus  : 


Isomers.  The  acids  of  the  acetic  series  show  the  same 
isomerism  as  the  alcohols  containing  one  atom  of  carbon  less, 
since  they  are  formed  from  these  by  means  of  the  cyanides. 
Thus  there  exist  one  propionic  acid,  two  butyric  acids,  corre- 


(CH3.CO)CH3 


Acetone. 


154 


VI.  MONOBASIC  FATTY  ACIDS. 


spending  to  the  two  propyl  alcohols,  four  valeric  acids,  corre- 
sponding to  the  four  butyl  alcohols,  and  so  on.  For  C^qH2q02, 
211  isomeric  forms  are  possible.  Among  all  such  isomers  there 
is  always  only  one  normal  acid. 

On  the  other  hand,  the  number  of  isomeric  acids  with  n  carbon 
atoms  is  always  equal  to  that  of  the  isomeric  primary  alcohols  contain- 
ing the  same  number  of  atoms  of  carbon. 


Formic  Acid,  aciclum  formicum,  CH2O2,  {Samuel  Fischer  and 
John  Bay,  1670;  Margraf),  occurs  free  in  ants,  especially 
Formica  rufa,  in  the  processionary  caterpillar  (Bombyx  pro- 
cessionea),  in  the  bristles  of  the  stinging  nettle,  the  fruit  of 
the  soap  tree  (Sapindus  saponaria),  and  in  tamarinds  and  fir 
cones ;  also  in  small  quantity  in  various  organic  liquids,  in 
perspiration,  urine,  and  the  juice  of  flesh. 

Formation.  From  HON,  CHCI3,  CH3OH,  COg,  etc.,  (see 
general  methods  of  formation).  It  also  results  from  the  action 
of  sodium  amalgam  upon  ammonium  carbonate  or  alkaline 
hydrocarbonates,  etc. ;  by  the  dry  distillation  or  oxidation  of 
many  organic  substances,  e.g.  starch,  (Scheele) ;  also  by  decom- 
posing them — e.g.  sugar — by  concentrated  sulphuric  acid. 

Preparation.  1.  Carbonic  oxide  is  readily  absorbed  by  soda- 
lime  at  210°,  with  formation  of  sodium  formate  (Merz). 

2.  When  oxalic  acid  is  heated,  formic  acid  is  obtained  in 
small  quantity  together  with  carbonic  oxide,  carbonic  acid  and 
water,  and  the  same  effect  is  produced  by  the  direct  action 
of  sunlight  upon  its  aqueous  solution  containing  uranic 
oxide : 

C^H^O,  =  CO,  +  CH^O^. 

This  decomposition  is  best  effected  by  heating  oxalic  acid 
with  glycerine  to  100°-110°,  (Berthelot,  Lorin),  the  formic  acid 
produced  combining  with  the  glycerine  to  an  ether,  Monofor- 
min,  (see  p.  202) : 

C3H^)3  +  H.CaOH  =  (^s^K'^Q^l^Q^  +H,0. 

Glycerine.  \  ^ 

Monoformin. 


FORMIC  ACID. 


155 


The  monoformin  is  then  saponified  either  by  boiling  it  with 
excess  of  water  or  by  the  addition  of  more  oxalic  acid,  through 
the  water  of  crystallization  of  the  latter.  In  this  case  mono- 
formin and  carbon  dioxide  are  again  produced,  the  process 
repeating  itself  time  after  time,  a  very  small  amount  of 
glycerine  being  thus  sufficient  to  convert  considerable  quantities 
of  oxalic  into  formic  acid. 

Properties.  Colourless  liquid  which  solidifies  in  the  cold  and 
fumes  slightly  in  the  air.  M.  Pt.  +  9^;  B.  Pt.  99°;  Sp.  Gr. 
1*22.  Has  a  pungent  acid  and  ant-like  odour,  acts  as  a  power- 
ful corrosive,  and  produces  sores  on  the  soft  parts  of  the  skin. 
Is  stronger  than  acetic  acid  and  a  powerful  antiseptic.  De- 
composes completely  into  carbonic  oxide  and  water  when 
heated  with  cone,  sulphuric  acid : 

CH2O2   =    CO  +  H2O. 

Salts.  Potassium-,  HCOgK,  Sodium-,  HCOgNa,  and  Am- 
monium formate,  HCOgNH^,  form  deliquescent  crystals.  The 
first  two  go  into  oxalates  when  strongly  heated,  with 
evolution  of  hydrogen  (see  p.  231) ;  the  ammonium  salt  into 
formamide  and  water  at  1 80° : 

HCO2.NH4  =  H.CO.NH2  +  H2O. 
The  lead  salt,  Pb(HC02)2,  forms  glancing,  difficultly  soluble 
needles,  the  copper  salt,  Cu(HC02)2  +  ^HgO,  large  blue  mono- 
clinic  crystals,  and  the  silver  salt  colourless  crystals.  The 
last-mentioned  separates  silver  upon  warming,  consequently  a 
solution  of  nitrate  of  silver  is  reduced  when  heated  with  formic 
acid. 

The  easily  soluble  mercuric  salt,  IIg(HC02)2,  gives  up  carbonic  acid 
upon  being  gently  warmed,  and  goes  into  the  sparingly  soluble  mer- 
curous  salt,  Hg2(HC02)2j  which  separates  in  white  plates;  on  increasing 
the  temperature  further,  this  decomposes  in  its  turn  into  carbon  dioxide 
and  metallic  mercury.  Similarly  an  aqueous  solution  of  mercuric  chlor- 
ide is  reduced  by  formic  acid  to  the  mercurous  salt,  HggClg. 

Formic  acid  is  thus  a  strong  reducing  agent : 

HCO.OH  =  CO2  +  H2. 

It  decomposes  into  carbonic  acid  and  hydrogen  when  heated  alone  to 
160°,  or  when  brought  into  contact  with  finely  divided  rhodium. 


156 


VI.  MONOBASIC  FATTY  ACIDS. 


This  power  of  reduction  which  distinguishes  formic  acid  froni  all  its 
higher  homologues,  may  be  explained  by  its  close  relationship  to 
carbonic  acid,  and  also  by  the  aldehydic  character  which  one  can  read 
in  its  constitutional  formula,  H — 0 — CHO. 

Acetic  Acid,  acidum  aceticum,  G^Ufi^,  was  known  in  the 
dilute  form,  as  crude  wine  vinegar,  to  the  ancients.  Stahl 
prepared  the  concentrated  acid  about  1700.  Glauber  mentions 
wood  vinegar  (1648).  Its  constitution  was  established  by 
Berzelius  in  1814. 

Occurrence.  Salts  of  acetic  acid  are  found  in  various  plant 
juices,  especially  those  of  trees,  and  in  the  perspiration,  milk, 
muscles  and  excrementa  of  animals.  Ethers  of  acetic  acid 
also  occur,  e.g.  triacetin  in  croton  oil,  (see  p.  162,  and  also 
under  glycerine). 

Formation.  (See  p.  148  et  seq.)  Is  the  final  product  of  the 
oxidation  of  a  great  many  compounds,  and  also  of  their  treat- 
ment with  alkalies. 

The  following  synthesis  is  of  historical  interest.  Perchloro-ethylene, 
C2CI4,  which  is  prepared  from  CCI4,  i.e.  from  CI  and  CSg,  yields  with 
chlorine  in  presence  of  water  in  direct  sunlight  tri-chloracetic  acid, 
carbon  trichloride,  CgClg,  being  obviously  formed  as  intermediate 
product,  {Kolbe,  1843)  : 

CCI3— CCI3  +  2H2O  =  CCI3— CO2H  +3HC1. 

The  latter  acid  is  reduced  to  acetic  by  nascent  hydrogen,  (Melsens). 

Preparation.  1.  From  Alcohol.  A  dilute  aqueous  solution 
of  alcohol,  containing  up  to  15  p.c,  is  slowly  converted  into 
acetic  acid  on  exposure  to  the  air  and  in  presence  of  nitrogen- 
ous substances,  by  the  agency  of  a  micro-organism,  the 
"  mother  of  vinegar,"  acetic  ferment,  or  mycoderma  aceti. 
The  acetic  fermentation  is  manifested  in  the  souring  of  beer 
or  wine,  with  the  production  of  beer  or  wine  vinegar. 

Vinegar  is  an  aqueous  solution  of  acetic  acid,  usually  containing  only 
3  to  5  p.  c. ,  but  containing  also  small  quantities  of  alcohol,  of  the  higher 
acids,  e.g.  tartaric  and  succinic,  the  ethyl  ethers  of  the  acids,  albumin- 
ous matters,  etc.  It  is  manufactured  on  the  large  scale  either,  as  in 
France,  by  the  older  method  in  a  series  of  half -full  oaken  casks,  or  by 
the  newer  quick  vinegar  process,  [Schiitzenhach). 

2.  From  Wood.    The  dry  distillation  of  wood,  which  is  con- 


ACETIC  ACID. 


157 


ducted  in  cast-iron  retorts,  yields  (1)  gases,  e.g,  hydrogen  15 
p.c,  methane  11  p.c,  carbon  dioxide  26  p.c,  carbonic  oxide 
41  p.c,  and  higher  hydrocarbons  7  p.c.  ;  (2)  an  aqueous 
solution  known  as  pyroligneous  acid  which,  in  addition  to 
acetic  acid,  contains  methyl  alcohol,  acetone,  homologues  of 
acetic  acid,  and  strongly  smelling  combustible  products,  (em. 
pyreuma) ;  and  (3)  wood  tar,  which  contains  compounds  of 
the  nature  of  carbolic  acid.  The  pyroligneous  acid  is  worked 
up  for  acetic  acid  by  converting  it  into  the  sodium  or  calcium 
salt,  heating  these — the  former  up  to  its  melting  point  and 
the  latter  to  200° — to  get  rid  of  empyreumatic  substances,  and 
then  distilling  with  sulphuric  acid. 

Properties.  Acetic  acid  is  a  strongly  acid  liquid  of  pungent 
odour,  which  feels  slippery  to  the  touch  and  burns  the  skin,  and 
which  solidifies  in  the  cold  to  large  crystalline  plates  melting 
at  17°;  (Glacial  acetic  acid).  B.  Pt.  118°,  Sp.  Gr.  at  15°, 
1*055.  Its  vapour  burns  with  a  blue  flame.  When  mixed 
with  water,  contraction  and  consequent  increase  in  density 
ensue,  the  maximum  point  corresponding  with  the  hydrate 
CH3CO2H  +  H2O,  =  CH3C(OH)3,  (ortho-acetic  acid),  which 
contains  77  p.c.  acid  and  has  a  Sp.Gr.  of  1*075  at  15*5°;  after 
this  the  specific  gravity  decreases  with  further  addition  of 
water,  so  that  a  50  p.c.  acid  has  almost  the  same  density  as 
one  of  100  p.c.  The  amount  of  acid  present  in  a  solution  is 
determined  either  by  its  Sp.  Gr.,  this  contraction  being  borne 
in  mind,  or  by  titration.  The  vapour  density  near  the  boiling 
point  is  much  higher  than  that  required  by  theory,  but  is 
normal  above  250°.  The  acid  is  hygroscopic,  and  stable 
towards  chromic  acid  and  cold  permanganate  of  potash.  It 
dissolves  phosphorus,  sulphur  and  many  organic  compounds, 
is  corrosive,  and  gives  rise  to  painful  wounds  on  tender  parts 
of  the  skin. 

Salts.    All  the  neutral  salts  of  acetic  acid  are  soluble  in  water. 

Potassium  acetate,  KC2H3O2 ;  hygroscopic  colourless  plates. 
Acid  potassium  acetate,  C2H3O2K  +  C2H4O2,  crystallizes  from 
the  concentrated  acid  in  glancing  mother-of-pearl  plates.  A 
salt  of  the  composition  C2H3O2K  +  2C2H4O2  is  also  known. 


158 


VI.  MONOBASIC  FATTY  ACIDS. 


Sodium  acetate,  NaC2H302,  forms  transparent  easily  soluble 
rhombic  prisms,  (terra  foliata  tartari  crystallisabilis). 

Ammonium  acetate,  NH4C2H3O2,  resembles  the  potassium 
salt.  It  is  used  in  medicine  as  a  sudorific,  (Liquor  ammonii 
acetici).  Its  solution  loses  ammonia  on  evaporation,  and  it 
yields  acetamide  when  distilled. 

Ferrous  acetate,  Fe2(C2H302)4,  is  largely  used  in  the  form 
of  ^'  iron  liquor"  as  a  mordant  in  dyeing.  The  normal  ferric 
salt,  Fe2(C2H302\,,  which  is  employed  for  the  same  purpose, 
is  obtained  when  a  soluble  ferric  salt  is  mixed  with  sodium 
acetate.  Its  solution  is  deep  brown-red  in  colour,  and  deposits 
the  iron  as  basic  salt  when  heated  with  excess  of  water  : 

Fe,(C,H30)e  +  4H,0  =  Fe^  {  {gJ^^J^^^^  +  4C,HA- 

It  is  used  in  medicine  as    liquor  ferri  acetici." 

The  analogous  aluminium  acetate  is  only  known  in  solution, 
and  finds  a  wide  application  as  "  red  liquor  "  mordant  in  calico 
printing  and  dyeing.  Its  use  depends  upon  its  easy  decom- 
posability  by  water,  e.g.  when  exposed  to  the  action  of  steam, 
and  on  the  affinity  of  the  residual  alumina  com]3ound  for  the 
colouring  matter.  It  is  employed  in  small  doses  as  an 
astringent  in  cases  of  diarrhoea,  etc. 

Lead  salts.  (1)  Neutral  lead  acetate  or  sugar  of  lead, 
Pb(C2H302)2  +  3H2O,  is  manufactured  from  sheet  lead  and 
acetic  acid.  It  forms  colourless  glancing  four-sided  prisms, 
which  are  poisonous  and  of  a  nauseous  sweet  taste.  It  com- 
bines with  lead  oxide  to 

(2)  Basic  salts  of  alkaline  reaction,  termed  sub-acetates. 

The  simplest  basic  salt  has  the  composition  Pb<^|^J^  q  ^ 

but  there  also  exist  others,  e.g.  pv,]^0  etc. 

•^K(0,H30,) 

Two  molecules  of  acetic  acid  can  combine  with  as  many  as 
five  molecules  of  lead  oxide.  These  basic  acetates  are  used  as 
Goulard's  lotion,  and  on  the  large  scale  for  the  preparation  of 
lead  white,  etc. 


PROPIONIC  AND  BUTYRIC  ACIDS. 


159 


Cupric  acetate,  Cu(G2H302)2  +  2H2O,  dark  green  easily 
soluble  crystals,  also  forms  basic  salts  (Verdigris).  It  yields 
double  salts  with  cupric  arseniate,  e.g.  Schweinfurth  green. 

Silver  acetate,  AgOgHgOg,  is  a  well  characterized  salt  of 
acetic  acid  ;  glancing  needles. 

Detection  of  acetic  acid.  (1)  Upon  heating  an  acetate  with  alcohol 
and  sulphuric  acid,  the  pleasant  smelling  ethyl  acetate  is  formed  ;  (2) 
By  means  of  the  silver  salt ;  (3)  By  the  odour  of  cacodyl  produced  upon 
heating  the  potassium  or  sodium  salt  w  ith  AsgOg. 

Propionic  acid,  =  CH3— CH^— CO^H.  {GoUlieh, 

1844.) 

Formation,  From  acrylic  and  lactic  acids  (see  p.  150);  also 
from  lactate  or  malate  of  calcium  by  suitable  schizomycetes 
fermentation,  {Fitz), 

Preparation.  By  the  saponification  of  ethyl  cyanide  (pro- 
pionitrile),  (1847).    (See  pp.  149  and  108.) 

Calcium  chloride  separates  it  from  its  aqueous  solution  in 
the  form  of  an  oil,  whence  its  name  TrpiaTosy  the  first,  and  ttlojv, 
fat ;  the  first  oily  acid. 

Butyric  acids,  C4Hg02. 

(1)  Normal  Butyric  acid,  fermentation  butyric  acid,  propyl- 
carbonic  acid,  CH3 — CH2 — CH2 — CO2H. 

Occurrence,  Free  in  perspiration,  in  the  juice  of  flesh,  in  the 
contents  of  the  great  gut,  and  in  the  solid  excrementa ;  as 
hexyl  ether  in  the  oil  of  the  fruit  of  Heracleum  giganteum,  as 
octyl  ether  in  Pastinaca  sativa,  and  to  the  extent  of  2  p.c. 
as  glycerine  ether  in  butter,  (Chevreul,  1822). 

Formation.  (See  also  general  modes  of  formation.)  Is  pro- 
duced by  the  decay  of  moist  fibrin  and  of  cheese  (being 
therefore  contained  in  Limburg  cheese),  by  a  Schizomycetes 
fermentation  of  glycerine,  and  especially  by  putrefaction  and 
fermentation  in  neutral  liquids,  {Pelouze  and  Gelis,  see  below). 
Further,  by  the  oxidation  of  albuminates  with  chromic  acid,  of 
fats  with  nitric  acid,  of  conine,  etc.,  and  also  by  the  dry  distil- 
lation of  wood. 

Prejjaration.  In  the  "butyric  fermentation"  of  sugar  or 
starch  by  fission  ferments  (Schizomycetes^  especially  Bacillus 


160 


VI.  MONOBASIC  FATTY  ACIDS. 


subtilis),  CaCOg  or  ZnO  being  added  at  the  same  time,  to 
combine  with  the  acid  formed.  Lactic  and  carbonic  acids 
(see  lactic  fermentation)  are  first  produced  here,  and  then 
butyric  acid,  with  evolution  of  hydrogen. 

Properties.  Thick  liquid  of  unpleasant  rancid  odour,  in  pre- 
sence of  ammonia  like  that  of  perspiration,  miscible  with  water, 
and  separating  from  the  aqueous  solution  on  the  addition  of 
salts.  B.  Pt.  163°.  Difficultly  oxidizable.  The  calcium  salt, 
Ca(C4H^02)2  +  H2O,  forms  glancing  plates,  and  is  characterized 
by  being  more  soluble  in  cold  than  in  hot  water ;  it  therefore 
separates  on  warming  the  concentrated  cold  aqueous  solution. 
On  prolonged  heating  of  the  solution,  however,  it  is  trans- 
formed into  the  Oa  salt  of  iso-butyric  acid.  The  silver  salt, 
Ag(C4H^02),  crystallizes  in  glancing  plates,  slightly  soluble  in 
water. 

(2)  Iso-butyric  acid,  di-methyl-acetic  acid,  iso-propyl-formic 
acid,  (CH3)2=CH— CO2H.  Is  present  in  the  free  state  in  the 
carob  (Bedtenbacher),  in  the  root  of  Arnica  montana,  and  as 
ether  in  Pastinaca  sativa  and  Roman  camomile  oil. 

It  is  obtained  from  isopropyl  cyanide  (Erlenraeyer),  by  the 
oxidation  of  isobutyl  alcohol,  by  the  aceto-acetic  ether  syn- 
thesis (p.  150),  etc.  It  is  very  like  fermentation  butyric  acid, 
but  is  more  sparingly  soluble  in  water  (1  in  5),  and  boils  9° 
lower,  i.e.  at  154°.  Unlike  the  latter,  however,  it  is  easily 
oxidized  to  acetone  or  acetic  acid,  and  carbonic  acid. 

The  existence  of  isobutyric  acid  was  predicted  by  Kolbe  in  1864  upon 
theoretical  grounds.  The  calcium  salt,  Ca(C4H702)2,  differs  from  its 
isomer  in  being  more  soluble  in  hot  water  than  in  cold. 

Valeric  acid,  C5H^q02,  exists  in  the  four  different  modifica- 
tions which  are  theoretically  possible  : 

(1)  Normal  Valeric  acid,  propyl-acetic  acid,  CH3— (CH2)3 — CO2H, 
from  normal  butyl  cyanide,  {Lieben  and  Rossi,  1871),  Is  best  prepared 
from  propyl-malonic  acid.  (See  malonic  acid  synthesis.)  B.  Pt.  185°. 
Only  soluble  in  27  parts  of  water. 

(2)  Iso-valeric  acid,  ordinary  valeric  acid,  isopropyl- acetic  acid, 
isohutyl-forndc  acid,  (CH3)2=CH — OHg — CO2H,  results  from 
isobutyl  cyanide.    It  is  found  in  the  free  state  and  in  the  form 


VALERIC  ACIDS,  ETC. 


]61 


of  ethers  in  the  animal  kingdom  and  in  many  plants,  especially 
(free)  in  the  valerian  root  (Valeriana  officinalis),  and  in  the 
angelica  root  (Angelica  arch  angelica),  from  which  it  is  obtained 
by  boiling  with  soda ;  further,  in  the  blubber  of  the  dolphin 
(Chevreul,  1817),  in  the  berries  of  Viburnum  opulus,  in  the 
perspiration  from  the  foot,  etc.  The  natural  acid  is  usually 
mixed  with  the  active  valeric  acid,  and  is  therefore  optically 
active ;  the  oxidation  of  fermentation  amyl  alcohol  by  chromic 
acid  yields  a  similar  mixture.  When  pure  it  is  optically 
inactive.  B.  Pt.  175°.  It  has  an  unpleasant  pungent  acid 
odour,  like  that  of  old  cheese,  and  a  corrosive  action.  It  is 
used  in  medicine.    Forms  a  hydrate  with  water. 

(3)  Methyl- ethyl-acetic  acid,  active  valeric  acid,  ^  jj^^CH— COgH, 

occurs  in  nature,  as  already  mentioned,  and  results  from  the  oxidation 
of  the  active  ( — )  amyl  alcohol ;  it  is  in  this  case  (  + )  optically  active, 
while,  if  prepared  synthetically,  e.g.  by  the  aceto-acetic  ether  reaction, 
it  is  optically  inactive.    (See  Tartaric  acid.)    B.  Pt.  175°. 

(4)  Tri-methyl-acetic  acid,  pivalic  acid,  (CHgjg^C — CO2H,  can  be 
prepared  from  tertiary  butyl  cyanide,  [Butlerow,  1873).  M.  Pt.  35°, 
B.  Pt.  164°.    Has  an  odour  like  that  of  acetic  acid. 

Of  the  Hexylic  acids,  eight  are  theoretically  possible,  and  of  these 
seven  are  already  known.  The  most  important  among  them  is  normal 
caproic  acid,  CH3— (€112)4 — COgH  {Chevreul,  1822),  which  is  found  in 
nature,  e.g.  in  cocoa-nut  oil,  Limburg  cheese,  and  as  glycerine  ether  in 
the  butter  made  from  goats'  milk,  and  is  produced  in  the  butyric  fer- 
mentation of  sugar,  and  by  the  oxidation  of  albuminous  compounds  and 
of  the  higher  fatty  acids,  etc.  Like  valeric  acid,  it  has  a  very  un- 
pleasant and  persistent  odour  of  perspiration  and  rancid  butter.  B.  Pt. 
205°. 

The  higher  acids  which  are  found  in  nature  are  all  of 
normal  constitution  (see  p.  144),  and  contain  for  the  most  part 
an  even  number  of  carbon  atoms.  Goats'  butter  contains  the 
acids  Cg,  Cg,  and  C^q,  hence  the  names  Caproic,  Caprilic,  and 
Capric  acids,  and  cocoa  nut  oil — in  addition  to  those  three — 
the  acid  C^g-  This  last,  Laurie  acid, is  contained  more  especially 
in  oil  of  laurels  (Laurus  nobilis) ;  Myristic  acid,  C^^,  is  present 
in  oil  of  iris  and  nutmeg  butter  (from  Myristica  moschata) ; 
Arachidic  acid,  C20,  in  the  oil  of  the  earth  nut  (Arachis  hypo- 
gaea) ;  Behenic  acid,  Cgg)  in  oil  of  ben  (Moringa  oleifera) ; 

(506)  L 


162 


VI.  MONOBASIC  FATTY  ACIDS. 


Cerotic  acid,  G^^,  forms  in  the  free  state  the  chief  constituent 
of  bees-wax,  and  as  ceryl  ether  that  of  Chinese  wax ;  Theo- 
bromic  acid,  Cg^,  is  present  in  cocoa  butter.  Palmitic  acid, 
G-^oR^fi^,  and  Stearic  acid,  G-^^H^qO^  (pp.  148  and  202),  are 
very  widely  distributed,  being  nearly  always  accompanied  by 
a  third  acid  poorer  in  hydrogen,  viz.  Oleic  acid,  C^gHg^Og 
(see  p.  166). 

Most  animal  and  vegetable  fats  and  oils,  e.g.  tallow,  suet, 
butter,  palm,  olive  and  seal  oils,  consist  almost  entirely  of  a 
mixture  of  the  glycerine  ethers  of  palmitic,  stearic  and  oleic 
acids,  these  ethers  being  termed  for  the  sake  of  brevity, 
Palmitin,  C3H5(OCi6H3iO)3,  Stearin,  C3H5(OCi8H350)3,  and 
Olein,  03115(0018^330)3.  Palmitin  and  stearin  being  solid 
and  olein  liquid,  the  consistence  of  a  fat  or  oil  depends  on  the 
preponderance  or  otherwise  of  the  solid  ethers. 

The  constitution  of  the  fats  was  elucidated  by  Chevreul  in 
1811. 

Most  of  the  varieties  of  wax  are  on  the  contrary  ethers 
of  monatomic  alcohols;  thus  bees'  wax  consists,  besides 
of  free  cerotic  acid,  of  the  melissic  ether  of  palmitic  acid, 
C3QHgi(OOi(jH3iO),  Chinese  wax  (from  Oroton  Sebiferum,  the 
tallow  tree)  of  the  ether  0271155(002711530),  and  spermaceti, 
(Oetaceum,  in  the  skull  of  Physiter  macrocephalus),  of  the 
ether  CieH33(O.CieH3iO). 

From  all  these  ethers  the  acids  are  obtained  in  the  form  of 
potassium  salts  by  saponification  with  alcoholic  potash,  thus  : 

C3H,(O.C,3H3,0)3  +  3KOH  =  3Ci3H3,0,K  +  03H,(OH)3. 

^  Y  ^  y  —  Y  ' 

Stearin.  Potassic  stearate.  Glycerine, 

The  separation  of  the  acids  is  effected  by  fractional  crystallization, 
fractional  precipitation  with  magnesium  acetate,  or  by  fractional  distil- 
lation either  of  the  fats  themselves  or  of  their  ethers  in  a  vacuum.  Oleic 
acid  can  be  separated  from  palmitic  and  stearic  by  taking  advantage  of 
the  solubility  of  its  lead  salt  in  ether. 

The  stearine  candles  of  commerce  consist  of  a  mixture  of 
palmitic  with  excess  of  stearic  acid,  some  paraffin  or  wax  being 
usually  added  to  prevent  them  becoming  crystalline.  The 
manufacture  of  candles  depends  upon  the  saponification  of  the 


SOAPS;  PALMITIC  AND  STEARIC  ACIDS,  ETC.  163 


solid  fats,  especially  of  beef  and  mutton  tallow,  by  means  of 
w  ater  and  lime  or  of  concentrated  sulphuric  acid. 

Soaps  consist  of  the  alkaline  salts  of  palmitic,  stearic  and 
oleic  acids,  hard  soaps  containing  soda  salts,  chiefly  of  the  solid 
acids,  while  soft  soaps  contain  potash  salts,  principally  oleate. 
By  the  addition  of  common  salt  to  a  solution  of  a  potash  soap, 
the  latter  is  converted  into  a  soda  soap,  which  is  insoluble  in 
a  solution  of  sodium  chloride.  The  potash  soaps  dissolve  to  a 
clear  solution  in  a  little  water,  but  dissociate  with  excess  of 
water  into  free  alkali  and  free  fatty  acid  or  acid  salt,  analogous 
to  super-acetate  of  potassium.  Upon  this  the  action  of  soaps 
depends.  The  calcium,  barium  and  magnesium  salts  are 
insoluble  in  water,  but  partly  crystallizable  from  alcohol. 
The  lead  salts  are  prepared  by  boiling  fats  with  lead  oxide 
and  water,  and  form  the  so-called  plaisters  or  lead  plaisters. 

The  higher  acids  with  an  uneven  number  of  carbon  atoms,  Cn,  C13, 
Ci5,  and  C17,  are  prepared  synthetically  from  the  acids  containing 
one  atom  of  carbon  more,  by  transforming  them  into  the  ketones, 
Cn_iH2n-i  .  CO  .  CH3,  and  oxidizing  these,  {Krafft),  see  p.  144. 

Normal  nonylic  acid,  C9H18O2,  can  be  got  from  normal  octyl  alcohol 
l)y  the  nitrile  reaction,  and  also  from  many  other  substances,  e.g.  by 
the  oxidation  of  oleic  acid  and  oil  of  rue  (p.  144).  It  is  present  in 
Pelargonium  roseum,  and  is  therefore  also  called  pelargonic  acid. 

Undecylic  acid,  C11H22O.2,  is  obtained  by  the  reduction  of  undecylenic 
acid,  C11H20O2,  which  latter  is  prepared  by  the  distillation  of  castor  oil 
in  a  vacuum. 

Palmitic  acid,  G-^oRc^^^^y  most  conveniently  prepared  from 
palm  oil,  which  is  a  mixture  of  palmitin  and  olein,  also  by 
fusing  oleic  acid  or  cetyl  alcohol  with  potash. 

Stearic  acid,  G^^H^fi^^y  from  the  so-called  shea-butter 

or  from  mutton  suet. 

Hepta-decylic  or  Margaric  acid,  C17H34O2,  was  formerly  believed  to 
be  present  in  fats,  but  this  was  afterwards  found  to  be  a  mixture  of  the 
acids  Cjg  and  Cjs,  (see  p.  29).  It  can  be  prepared  synthetically,  e.g. 
from  cetylic  cyanide,  CjgH33.CN. 

Cerotic  acid,  C27Hg402,  and  the  higher  molecular  acids  in  general, 
result  upon  fusing  the  corresponding  primary  alcohols  with  potash,  i.e. 
from  their  oxidation. 

Melissic  acid  appears  from  the  most  recent  investigations  to  have 
the  formula  CgiHggOg. 


164  VI.  MONOBASIC  FATTY  ACIDS. 


B.  Unsaturated  Acids,  C„H2^_202. 


M.  Ft. 

B.  Pt 

M.  Pt. 

Acrylic  acid,  C3H4O2 

r 

140° 

Pyr  oterebic  acid,  CgHiQO. 

fi 

182° 

Crotonic  acids,  C4HgO.^-^  2 

172° 

Hypogaeic  acid,Ci6H3oO. 

33° 

'is 

16° 

160° 

Angelic  acid,  etc. ,  CgHgOg 

45° 

185° 

Oleic  acid,  ^^18113402 

14"=* 

These  acids  are  known  as  the  acids  of  the  oleic  series.  In 
their  physical  properties  they  nearly  resemble  the  saturated 
acids,  apart  from  differences  in  melting  point  which  are  some- 
times considerable ;  and  they  also  behave  as  acids  in  an 
analogous  manner,  but  differ  characteristically  in  that  they  are 
capable  of  combining  either  with  two  atoms  of  hydrogen, 
when  heated  with  hydriodic  acid,  or  with  two  atoms  of  halogen 
or  one  molecule  halogen  hydride,  to  form  the  saturated  acids 
or  their  substitution  products.  Thus  oleic  acid,  C^gHg^Og, 
when  treated  with  hydriodic  acid  and  phosphorus,  yields  stearic 
acid,   CjgHggOg,  and  with   bromine,   dibromo-stearic  acid, 

In  this  way  they  characterize  themselves  as  derivatives  of  the 
unsaturated  hydrocarbons  of  the  ethylene  series,  from  which  one  may 
imagine  them  to  result  by  the  replacement  of  an  atom  of  hydrogen  by 
carboxyl.    (Olefine-carboxylic  acids. ) 

Upon  the  addition  of  halogen  hydride,  the  halogen  does  not  always 
attach  itself  to  that  carbon  atom  to  which  the  least  hydrogen  is  bound. 

Modes  of  formation.  1.  By  oxidation  of  the  corresponding 
alcohols  or  aldehydes,  e.g.  acrylic  acid  from  allyl  alcohol  or 
acrolein. 

2.  From  the  unsaturated  alcohols  or  their  iodides,  by  con- 
verting them  into  the  cyanides  and  saponifying  these,  e.g. 
crotonic  acid  from  allyl  iodide. 

Both  these  methods  of  formation  are  analogous  to  those  of  the  fatty 
acids. 

3.  From  the  mono-halogen  substitution  products  of  the 
saturated  fatty  acids,  by  warming  with  alcoholic  potash,  some- 


THE  OLEIC  ACID  SERIES. 


165 


times  upon  simply  heating  with  water.  This  is  analogous  to 
tlie  formation  of  the  olefines  from  halogen-alkyl. 

4.  From  the  acids  of  the  lactic  series  by  separation  of  water, 
thus  : 

CHoCOH)— CH2— COOH  =  CH2=CH— CO2H  +  H^O. 

 Y  Y  ;  

Ethylene  lactic  acid.  Acrylic  acid. 

This  reaction  corresponds  with  the  formation  of  the  olefines 
from  monatomic  alcohols. 

Constitution  and  Isomers.  The  constitution  of  the  unsaturated 
acids,  OnH2a_202,  is  given  when  they  are  regarded  as  olefin e- 
carboxylic  acids.  As  many  isomeric  acids  as  unsaturated 
alcohols  of  n — 1  carbon  atoms  are  therefore  possible.  (See 
mode  of  formation  2,  and  cf.  crotonic  acid.) 

The  position  of  the  double  bond  is  established  by  fusing  the 
acids  with  potash  or  soda,  i.e.  by  oxidizing  them.  Oxidation 
occurs  at  the  point  of  the  double  bond,  (cf.  p.  48),  and  leads 
to  the  formation  of  2  mols.  of  \  monobasic  fatty  acidf  e.g.  : 
CHg-CH^CH-CO^H  +  2K0H  +  0  =  2CH3-CO2K  +  H^O. 

Other  oxidizing  agents,  such  as  chromic  and  nitric  acids, 
also  break  them  up  for  the  most  part  in  a  similar  manner,  but 
they  carry  the  oxidation  further. 

By  cautious  oxidation,  on  the  other  hand,  e.g.  with  KMn04  in  the 
cold,  the  elements  of  hydrogen  peroxide  are  simply  added,  and  there 
are  formed  di-oxy-acids  (p.  219)  containing  an  equal  number  of  carbon 
atoms,  for  instance,  dioxy-stearic,  Ci8H34(OH)20.2,  from  oleic  acid. 

Acrylic  acid,  ethylene  -  carhoxylic  acid,  CgH^Og,  = 
CHg^OH — COgH,  (Redtenbacher),  Is  prepared  by  the  oxida- 
tion of  acrolein  by  oxide  of  silver,  or  by  the  distillation  of  /3-iodo- 
propionic  acid  with  oxide  of  lead.  (Cf.  mode  of  formation 
3.)  It  is  very  similar  to  propionic  acid.  M.  Pt.  +  7°,  B.  Pt. 
139°- 140°.  Miscible  with  water  and  capable  of  polymerization. 
It  is  reduced  to  propionic  acid  when  warmed  with  zinc  and 
sulphuric  acid,  and  is  broken  up,  on  fusion  with  alkali,  into 
acetic  and  formic  acids. 

Crotonic  acids,   C4Hg02.      (1)    Ordinary  or  solid  crotonic  acid, 

CHy — CH=CH — CO2H,  occurs  along  with  iso-crotonic  acid  in  crude 
pyroligneous  acid,  and  is  prepared  from  allyl  iodidg  by  means  of  the 


166 


VL  MONOBASIC  FATTY  ACIDS. 


cyanide,  notwithstanding  that  one  would  expect  to  get  iso-crotonic  acid 
by  this  reaction.  Such  abnormal  reactions  are  termed  molecular  re- 
arrangements, and  they  are  explained  by  assuming  that  addition  pro- 
ducts are  first  formed,  from  which  atomic  groups  are  then  split  off,  in 
this  case  HCl : 

CH2-CH-CH2-CN  +  2H2O  =  CH2=CH-CH2-COOH  -f  NH3 ; 
CH2=CH— CH2— COOH  +  HCl  =   CH3— CHCl— CHg—COOH, 

=   CH3— CH=CH— CO2H  +  HCl. 

It  is  also  easily  prepared  by  heating  malonic  acid  with  para-aldehyde 
and  acetic  anhydride.  It  crystallizes  in  woolly  needles  or  large  prisms, 
M.  Pt.  72°,  B.  Pt.  189°,  has  an  odour  like  that  of  butyric  acid,  and 
is  fairly  soluble  in  water. 

(2)  Isocrotonic  acid,  CH2=CH— CH2— COgH,  which  is  present  in 
croton  oil,  is  liquid,  and  changes  into  ordinary  crotonic  acid  at 
170°-180°. 

(3)  Meth-acrylic  acid,  G^2=^<CcoiI 

is  found  in  small  quantity  in 

Roman  camomile  oil,  and  smells  like  decaying  mushrooms. 

When  fused  with  potash,  (1)  solid  crotonic  acid  yields  two  molecules 
of  acetic  acid,  (2)  isocrotonic  acid  yields  the  same,  by  a  molecular  re- 
arrangement, and  (3)  meth-acrylic  acid  yields  propionic  and  formic 
acids.    For  the  isomeric  relations,  see  B.  16,  2592. 

Angelic  acid,  C5H8O2,  =  C4H7.CO2H,  is  present  in  the  angelica  root, 
and,  together  with  tiglic  acid,  in  Roman  camomile  oil.  M.  Pt.  45°.  It 
differs  from  valeric  acid,  among  other  points,  by  its  state  of  aggrega- 
tion. Among  its  isomers  are  Tiglic  acid,  =  a-methyl-crotonic  acid,* 
CH3— CH=C(CH3)— CO2H,  and 

Allyl-acetic  acid,  CH2=CH— CH2— CH2— CO2H. 

Pyro-tereWc  acid,  C6H10O2,  =  {CH3)2=C=CH—CH2—C02H,  results 
from  the  distillation  of  terebic  acid,  C7H10O4,  and  Teracrylic  acid, 
C7HJ2O2,  from  that  of  terpenylic  acid,  C8H12O4, 

For  investigations  of  these  unsaturated  acids  and  their  isomeric 
relations,  still  in  part  unexplained,  see  Fittig,  A.  188,  42;  195,  56, 
128,  etc. 

Undecylenic  acid,  C11H20O2,  from  castor  oil.    (See  Undecylic  acid. ) 

Oleic  acid,  G-^^^fi^  (Ohevreul)^  is  present  as  olein  in  the 
fatty  oils  especially,  e.g.  olive,  almond  and  train  oils.  Colour- 
less oil,  solidifying  to  white  needles  in  the  cold.  M.  Pt.  14°. 
Cannot  be  volatilized  without  decomposition.  It  is  tasteless 
and  odourless,  and  has  no  action  upon  litmus,  but  quickly 
becomes  yellow  and  acid  by  oxidation  in  the  air,  and  also 

*  For  the  nomenclature  compare  the  names  of  the  substituted  fatty 
acids. 


THE  PllOPIOLIG  ACID  BERIKS. 


167 


acquires  a  rancid  odour.  It  yields  on  fusion  with  potash  the 
saturated  acids  C-^^QR^fi2  CgH^Og,  and  on  oxidation  with 
nitric  acid  the  acids  from  G^Rfi^  CJ^oHgoOg,  besides  dibasic 
acids. 

Nitrous  anhydride  converts  it  into  the  isomeric  crystaUine 
Elaidic  acid.    M.  Pt.  45°. 

Erucic  acid,  C22H42O2,  in  rape  seed  oil  (Brassica  campestris). 


Kelated  to  the  above  are  : 

Linoleic  acid,  CjgHggOg,  which  belongs  to  the  next  series,  and  which 
is  present  as  glycerine  ether  in  the  drying  oils,  e.g.  linseed,  hemp  and 
nut  oils ;  also  Ricinoleic  acid,  C13H34O3,  whose  glycerine  ether  forms 
castor  oil.  The  so-called  ricinoleic-sulphuric  acid,  which  is  prepared 
by  treating  castor  oil  with  sulphuric  acid,  is  extensively  used  in  the 
Turkey -red  manufacture. 

0.  Propiolic  Acid  Series,  O^Hgn-A. 

The  acids  of  this  series  again  contain  two  atoms  of  hydrogen 
less  than  those  of  the  former,  and  are  to  be  regarded  as  car- 
boxylic  acids  of  the  acetylene  hydrocarbons,  e.g.  propiolic  acid, 
CH=C — CO2H,  as  acetylene-carboxylic  acid.  They  can  ac- 
cordingly be  prepared  by  the  addition  of  GO^  to  the  sodium 
derivatives  of  the  acetylenes  (analogously  to  mode  of  formation 
4  of  the  saturated  acids,  p.  149). 

They  closely  resemble  the  unsaturated  acids  which  have 
been  already  described,  but  differ  from  them  by  their  cap- 
ability of  combining  first  with  two,  and  finally  with  four 
monovalent  atoms  of  hydrogen  or  halogen,  and  of  yielding  ex- 
plosive compounds  with  ammoniacal  silver  and  copper  solutions. 
There  are,  however,  acids  of  the  formula  CnHgn-A  which  do 
not  possess  this  last  peculiarity,  viz.,  those  which  are  derived, 
not  from  the  homologues  of  acetylene  proper,  but  from  their 
isomers,  and  which  therefore  contain  two  double  bonds  instead 
of  a  triple  one. 


The  most  important  member  of  the  series  is  Propiolic  or 
Propargylic  acid,  C3H2O2,  -  CH=C — CO^H,  which  corre- 
sponds to  propargyl  alcohol,  and  is  prepared  by  warming  an 


168 


VI.  MONOBASIC  FATTY  ACIDS. 


aqueous  solution  of  the  acid  potassium  salt  of  acetylene-di- 
carboxylic  acid,  the  latter  being  itself  obtained  from  dibromo- 
succinic  acid.  (See  p.  238,  also  B.  18,  677.)  In  its  physical 
properties  it  is  very  like  propionic  acid,  forms  silky  crystals 
below  6°,  and  boils  at  144°.  It  is  readily  soluble  in  water  and 
alcohol,  and  becomes  brown  in  the  air.  It  gives,  even  in 
dilute  solution,  the  characteristic  explosive  silver  precipitate, 
Tetrolic  acid,  C4H4O2,  and 

Sorbic  acid,  CgHgOg,  the  latter  of  which  is  contained  in  the  juice  of 
the  unripe  sorb  apple  (Sorbus  aucuparia),  have  both  relatively  high 
melting  and  boiling  points.  The  higher  acids  of  the  series  are  for  the 
most  part  distinguished  by  the  termination  "  olic,"  e.g,  Undecolic  acid, 
C11H20O2,  Palmitolic  acid,  CiqU^qO^,  Stearolic  acid,  C13H32O2,  Behenolic 
acid,  C22H4QO2 ;  they  result  from  the  corresponding  unsaturated  acids, 
CnH2u_202,  by  the  addition  of  Br^  and  separation  of  2HBr, 

Appendix,    A.  Di-acetylene-mono-carboxylic  acid, 

CH=C— C=C— CO2H  appears  to  exist.    (B.  18,  681,) 

D.  Halogen  Substitution  Products  of  the  Mono- 
basic Acids. 

The  saturated  monobasic  acids  yield  substitution  products 
when  acted  upon  by  chlorine  or  bromine,  or — better — bromine 
and  phosphorus,  e.g. ; 


M.Pt. 

B.  Pt. 

M.  Pt. 

B.  Pt. 

CH3— C02H 

Acetic  acid,    ,  . 

17° 

118° 

CH3 — CH2 — CO2H 
Propionic  acid,  . 

liq. 

140° 

CH2CI— CO2H 
Mono  chlor-acetic 
acid,  .... 

186° 

CH3— CHCl— COoH 
a-chloro-propionic 
acid,  .... 

liq. 

186° 

CHCI2— COOH 
Di  chlor-acetic 
acid,  .... 

liq. 

191° 

CH2CI— CH2— CO2H 
^-chloro  -propionic 
acid,  .... 

40° 

CCI3— COOH 
Tri-chlor-acetic 
acid,  .... 

52° 

195° 

CgHsBrg— CO2H 
Di-bromo-pro- 
pionic  acids,  etc. 

SUBSTITUTED  ACIDS.  169 


The  acids  poorer  in  hydrogen  also  yield  similar  substitution 
products  : 


M.  Pt. 

CH2=CH— CO2H 

7° 

CH=C— CO2H 
Propiolic  acid. 

CH2=CC1— CO2H 
a-Chlor-acrylic  acid,  .    .  , 

65° 

lodo-propiolic  acid,  etc. 

CHC1=CH— CO2H 
j8-Chlor-acrylic  acid,  ,    ,  . 

84° 

These  compounds  are  likewise  monobasic  acids,  being  often 
very  similar  to  the  mother  substance,  and  exceeding  it  in 
acidity.  Since  their  acid  nature  remains  unaltered,  they  still 
contain  the  carboxyl  group  ;  the  halogen  has  therefore  replaced 
the  hydrogen  of  the  hydrocarbon  radicle.  They  may  also  be 
looked  upon  as  haloid  substitution  products  of  the  hydro- 
carbons, in  which  one  atom  of  hydrogen  is  replaced  by 
carboxyl : 

01 

CH3 .  01,  Ohloro-methyl.    OHg  qq      Ohlor-acetic  acid. 

The  modes  of  formation  and  properties  of  these  substituted 
acids  also  coincide  with  this  view.  Thus,  while  they  show  a 
perfectly  analogous  behaviour  to  that  of  the  non-substituted 
acids,  forming  salts,  ethers,  chlorides,  anhydrides  and  amides, 
their  halogen  atoms  are  as  easily  exchangeable,  e.g.  for 
OH,  ON,  or  SO3H,  as  those  of  the  substitution  products  of 
the  hydrocarbons.    (See  p.  170.) 

Isomers  and  Constitution.  While  in  each  case  only  one  mono-, 
di-,  etc.,  haloid  acetic  acid  exists,  two  isomeric  mono-haloid 
propionic  acids  are  known  (see  table).  This  is  readily 
explicable  from  the  fact  that  in  propionic  acid, 

OH3-OH2— OO2H, 
P  a 


170 


VI.  MONOBASIC  FATTY  ACIDS. 


the  two  a-hydrogen  atoms  are  differently  bound  to  the  three 
/5-ones,  the  former  being  attached  to  the  carbon  atom  nearest 
to  the  carboxyl  and  the  latter  to  that  one  farthest  from  it. 
According  to  theory,  therefore,  with  which  the  observed  facts 
agree,  the  following  two  isomers  are  possible  : 

CH3— CHX— CO^H  and  CH^X— CH^— CO^H. 

^  Y  ^  Y  ^  ' 

a-Haloid-propionic  acid.         /3-Haloid  propionic  acid. 
These  acids  yield  two  isomeric  lactic  acids  by  exchange  of 
their  halogen  for  hydroxyl,  thus  : 

CH3— CH(OH)-CO,H  and  CH2(0H)— CH^— CO^H. 

Common  lactic  acid.  Ethylene-lactic  acid. 

The  constitution  of  both  of  these  lactic  acids  follows  from 
their  other  modes  of  formation,  (see  p.  214,  et  seq.).  The 
position  of  the  halogen  in  the  a-  and  j3-  substituted  propionic 
acids  is  thus  also  fixed. 

Those  substituted  acids  which  contain  the  halogen  bound  to  the  a- 
carbon  atom,  i.e.  to  the  carbon  atom  next  to  the  carboxyl,  are  termed  a- 
acids,  and  the  others  jS,  7,  etc.,  acids,  the  successive  carbon  atoms  in 
their  order  from  the  carboxyl  group  being  designated  as  a,  jS,  7,  etc. 

We  thus  distinguish,  for  instance,  between  a-,  jS-  and  7-  chloro- 
butyric  acids,  aa-,  a/5-  and       dibromo-propionic  acids,  etc. 

A  chlorinated  rormic  acid,  01 — COgH,  is  incapable  of 
existence ;  its  derivatives  are  described  as  derivatives  of 
chloro-carbonic  acid. 

Formation,    (a)  Of  the  saturated  substituted  acids  : 

1.  Ohlorine  and  bromine  can  substitute  directly. 

2.  From  oxy-acids  of  the  gly collie  series  by  the  action  of  PCI5,  HBr, 
etc. 

3.  By  the  addition  of  halogen  or  halogen  hydride  to  the  unsaturated 
acids. 

(b)  Of  the  unsaturated  substituted  acids  : 

e.g.  From  di-  or  poly-brominated  etc.  acids,  by  the  separation  of 
HCl,  HBr  or  HI. 

Behaviour.  1.  For  the  replacement  of  chlorine,  bromine, 
and  iodine  by  hydroxyl,  see  p.  169.  This  exchange  takes 
place  with  more  difficulty  in  the  a-mono-chloro-substituted 
acids  than  in  the  corresponding  bromine  and  iodine  com- 


SUBSTITUTED  FATTY  ACIDS. 


171 


pounds,  but  more  easily  than  in  the  case  of  the  chloro-alkyl 
compounds,  and  it  is  effected  by  means  of  moist  oxide  of 
silver,  or  frequently  by  prolonged  boiling  with  water  alone, 
(A.  200,  75).  In  this  way  monochlor-acetic  yields  glycollic 
acid: 

CHoCl  CHo .  OH 

I        +H2O  =  I  +HC1. 

CO2H  CO2H 

p.  Halogen  acids  on  the  other  hand  lose  halogen  hydride  upon  being 
boiled  with  water,  and  give  rise  to  unsaturated  acids,  together  with 
CO2  and  olefines  Cn_i.  7-Halogen  acids  break  up  under  these  condi- 
tions (even  with  cold  soda  solution)  into  HCl,  etc.,  and  a  lactone,  i.e. 
an  anhydride  of  a  7-oxy-acid,  (see  these  ;  c.f.  Fittig,  A.  208,  116). 

2.  Upon  heating  with  cyanide  of  potassium,  cyano-fatty 
acids  are  produced  : 

CH2CI— CO2K  +  KCN  =  CH2<^^  ^  +  KCl. 

Potassium  cyano-acetate. 

These  compounds  are  on  the  one  hand  monobasic  acids,  and 
on  the  other  cyanides,  i.e.  nitriles  of  the  acids,  and  they  conse- 
quently yield  dibasic  acids  upon  saponification,  in  the  above 

case  malonic  acid,  C5H2<^QQ^g 

3.  They  form  sulphonic  acids  with  sodium  sulphite,  e.g.  : 
CH2CI— CO^Na  +  Na-SOgNa  =  G^2<co^l  +  ^^(^i* 

Sodium  sulpho-acetate. 
These  latter  are  compounds  which,  apart  from  the  acid 
character  they  derive  from  the  carboxyl,  are  actual  sulphonic 
acids,  like  ethyl-sulphonic  acid,  and  are  thus  dibasic.  Their 
sulpho-group  can  however  be  replaced  by  OH  on  boiling  with 
alkalies. 

4.  With  AgNOg,  under  favourable  conditions,  nitro-derivatives  of 
the  fatty  acids  are  formed,  which  yield  amido-acids  on  reduction,  (p. 
212). 

Iso-nitroso  derivatives  of  the  fatty  acids,  e.g.  a-iso-nitroso-propionic 
acid,  CH3 — C(N.OH) — COgH,  are  also  known  ;  they  are  formed  by  the 


172 


VI.  MONOBASIC  FATTY  ACIDS. 


action  of  hydroxylamine  on  the  ketonic  acids,  for  instance,  pyroracemic 
acid,  CH3 — CO— CO2H,  and  also  yield  amido- acids  upon  reduction. 

The  compounds  mentioned  under  1  and  3  are  to  be  regarded 
as  derivatives  of  the  alcoholic  acids,  just  as  the  nitro-alkyls, 
alkyl  cyanides,  and  alkyl-sulphonic  acids  are  derivatives  of 
the  alcohols. 


The  chlorinated  acetic  acids  are  formed  by  the  direct  substitution  of 
acetic  acid,  or  better,  of  acetyl  chloride,  chlorinated  acetyl  chlorides 
ensuing  in  the  latter  case  as  intermediate  products. 

Mono  chlor-acetic  acid,  CH2OI.CO2H,  is  got  by  chlorinating  acetic 
acid,  preferably  in  the  presence  of  acetic  anhydride.  It  forms  rhombic 
prisms  or  tables  and  corrodes  the  epidermis. 

Di-chlor-acetic  acid,  CHCI2.CO2H,  is  more  conveniently  obtained  by 
warming  chloral  hydrate  with  potassium  cyanide,  (B.  lO,  2120),  and 

Tri-chlor-acetic  acid,  COI3.CO2H,  by  oxidizing  chloral  hydrate  with 
nitric  acid.  The  former  decomposes  with  boiling  alkali  to  oxalic  and 
acetic  acids,  and  the  latter  to  chloroform  and  carbon  dioxide.  Back- 
ward substitution  reconverts  tri-,  di-,  and  mono-chlor-acetic  acids  into 
aeetic  acid,  {Melsens,  1842). 

The  Bromo-  and  lodo-acids  are  analogous  to  the  above. 

a-CMoro -propionic  acid,  CH3 — CHCl — COgH,  is  obtained  by  the 
action  of  POI5  upon  lactic  acid,  and  decomposition  of  the  lactyl  chloride, 
CH3— CHCl— COCl,  at  first  formed,  by  water. 

jS-Iodo-propionic  acid,  CH2I — CHg — CO2H,  is  prepared  by  acting 
upon  glyceric  acid,  CHglOH)— CH(0H)~C02H,  with  iodide  of  phos- 
phorus, (exchange  of  20H  for  21  and  of  I  for  H) ;  also  by  acting  on 
acrylic  acid  with  hydriodic  acid.  It  forms  colourless  six-sided  tables 
of  a  peculiar  odour  ;  M.  Pt.  82°. 

Sulpho-acetic  acid,  CH2(S03H)— COgH.  Deliquescent  prisms  con- 
taining IJ  mols.  HgO  of  crystallization  ;  yields  salts  which  crystallize 
well. 

Cyan-acetic  acid,  CH2{CN)— CO2H,  is  a  crystalline  substance  melting 
at  65° -66°  and  easily  soluble  in  water  ;  it  decomposes  into  aceto-nitrile, 
CH3  — CN,  and  CO2  upon  heating,  and  yields  malonic  acid  on  saponifi- 
cation. 

The  two  Cyano -propionic  acids,  C2H4(CN) — CO2H,  give  the  two 
succinic  acids  when  saponified. 

jS-Nitro -propionic  acid,  CHolNOg) — CH2— COOH,  forms  glancing 
scales,  melting  at  67°,  and  easily  soluble  in  water,  alcohol  and  ether. 

Nitro-acetic  acid,  CHgtNOg) — COgH  is  only  known  as  ethyl  ether. 


ACID  DERIVATIVES.  173 

VII.  ACID  DERIVATIVES. 

Summary. 

Acetic  acid 
Sodium  acetate 
Ethyl  acetate 

Acetic  anhydride 

Acetyl  chloride 
Thiacetic  acid 
Acetamide 


These  derivatives  result  by  methods  of  which  some  are 
perfectly  analogous  to  the  modes  of  formation  of  the  corre- 
sponding alcoholic  derivatives,  but  they  differ  characteristic- 
ally from  these  by  being  less  stable  towards  saponifying 
agents. 

A  number  of  other  derivatives,  viz.,  amido-  and  imido- 
chlorides,  thiamides,  imido-thio-compounds  and  amidines  are 
peculiar  to  the  acids  : 

Imido-compounds 
Imido-thio-  ,, 
Amidines 

*  R  signifies  an  alcohol  radicle  or  an  analogous  group  such  as  CgHg — , 
phenyl.    (See  aromatic  compounds.) 

These  compounds  are  also  characterized  by  being  easily 
saponifiable. 


CA.OH 

CaHg.ONa 

C^Hs.O.CC^Hg) 
or 


>0 


C2H5.CI 
C2H5.SH 


Alcohol 

Sodium  ethylate 
Ethyl  ether 

Ethyl  chloride 
Mercaptan 
Ethylamine 


C2H3O.OH 
CgHaO.OlSra 

C2H3O 

C2H3O.CI 
C2H3O.SH 

an.o.NH, 


CH3— CCI2-NHR* 

CH3— CC1=:NR 

CH3-CS.NH2 


Amido-chlorides 
Imido-chlorides 
Thiamides 


CH3— C(NH)OH 
CH3-C(NH)SR 
CH3— C(NH)(NH2 


174 


VII.  ACID  DERIVATIVES. 


A.  Ethers  of  the  Fatty  Acids. 

By  the  replacement  of  the  typical  hydrogen  of  a  fatty  acid 
by  an  alcohol  radicle,  ethers  are  produced  which  are  perfectly 
analogous  to  the  ethers  of  the  mineral  acids  in  their  properties, 
and  which  are  also  obtained  by  analogous  methods.  Since 
these  correspond  to  the  salts  of  the  acids,  they  are  often 
designated  in  a  similar  way,  e,g.  acetic  ethyl  ether  =  "  ethylic 
acetate." 

Modes  of  formation.  (1)  By  direct  action  of  the  acid  upon  the 
alcohol : 

C2H5.OH  +  C2H3O.OH  =  C2H5.O.C2H3O  +  H2O. 

Ethylic  acetate. 

Only  a  few  acids  thus  react  with  alcohol  by  itself  to  form 
ethers  in  quantity,  for  reasons  similar  to  those  already  given 
for  mineral  acids  at  p.  98. 

In  the  preparation  of  ethers  it  is  therefore  necessary  to  provide  against 
a  re- saponification  of  the  ether  after  it  is  formed,  which  is  done  as  above 
described  (loc.  cit.).  The  method  of  etherification  by  leading  hydro- 
chloric acid  gas  into  a  mixture  of  acid  and  alcohol  is  especially  appli- 
cable. The  ethers  are  also  obtained  directly  from  the  acid  nitriles  by 
passing  hydrochloric  acid  into  their  warm  alcoholic  solution.  The 
limit  of  etherification  agrees  with  the  Guldherg-  Waage  law  of  the  action 
of  mass,  [Berthelot,  Menschutkin.) 

(2)  By  the  action  of  the  acid  chlorides  upon  the  alcohols  or 
their  sodium  compounds  (cf.  p.  99) : 

C2H30.C1  +  C2H,.0H  =  C2H3O.O.C2H5  +  HCI. 

(3)  By  the  action  of  the  halogen  alkyls  upon  the  salts  of 
the  acids  (cf.  p.  99) : 

C2H5Cl  +  C2H30.0Na  =  C2H5.0.(C2H30)  +  NaCl. 

Ethers  are  likewise  obtained  by  heating  the  salts  of  fatty  acids  with 
alkyl  sulphates. 

Properties.  The  ethers  of  the  monobasic  fatty  acids  are  for 
the  most  part  neutral  liquids  which  volatilize  without  decom- 
position, only  those  of  them  which  contain  a  small  number  of 
carbon  atoms  in  the  molecule  being  soluble  in  water,  e.g,  acetic 


ETHERS  OF  THE  FATTY  ACIDS. 


175 


(^t  lier  (1  : 14).  They  undergo  saponification  upon  heating  or, 
more  generally,  superheating  with  water,  or  upon  boiling  with 
alkalies  or  acids. 

It  often  suffices  for  saponification  simply  to  mix  the  ether  with  alco- 
holic potash  or  soda,  or  to  allow  it  to  stand  for  a  lengthened  period 
with  water. 

The  compound  ethers  are  very  active  chemically,  since  they 
readily  exchange  the  group  — OCgH^,  i.e.  — OR,  for  another 
group,  yielding  with  ammonia,  for  instance,  amides  (p.  180). 
Phosphorus  pentachloride  decomposes  them  into  the  chloride 
of  the  alcohol  and  that  of  the  acid,  the  oxygen  of  the  hydroxyl 
being  exchanged  for  two  atoms  of  chlorine.  Sodium  methylate 
combines  with  the  ethers  to  form  unstable  compounds, 
/ONa 

R — C^OCHo,  which  are  derivatives  of  ^'ortho  acids."  (See 
\0R' 

p.  149;  also  B.  20,  646.) 

The  odour  and  taste  of  many  of  the  ethers  is  so  agreeable 
that  they  are  manufactured  upon  a  large  scale,  and  employed 
as  fruit  ethers  or  fruit  essences. 

Ethyl  formate,  formic  ethyl  ether,  H.CO.OC2H5.  B.  Pt.  55^  Is 
employed  in  the  manufacture  of  artificial  rum  or  arrak. 

Ethyl  acetate,  acetic  ether,  C2H3O.  OCgHg.  B.  Pt.  75°.  Is  used  inter- 
nally as  a  medicine. 

Amyl  acetate,  CgHgO.OCgHn.  B.  Pt.  148°.  The  alcoholic  solution 
of  this  forms  the  ether  of  pears. 

Ethyl  butyrate,  C4H7O.OC2II5,  is  the  ether  of  pine  apples. 

Iso-amyl  iso-valerate,  C5H9O.OC5H11,  B.  Pt,  196°,  finds  application 
as  apple  oil  or  apple  ether. 

Cetyl  palmitate,  CieHgiOalC^eHgg),  Ceryl  cerotate,  C)27^5'a02{C^7B^^), 
and  Mellissic  palmitate,  C^eHsiOglOgoHgi).    (See  Wax  Varieties,  p.  162.) 

AVhen  the  ethers  of  the  acids  of  high  molecular  weight  are  distilled 
under  the  ordinary  pressure  and  not  in  a  vacuum,  they  break  up  into 
olefine  and  fatty  acid.    (See  p.  49.) 

Among  the  ethers  of  the  haloid-substitution  acids  may  be 
mentioned  ethyl  monochlor-acetate,  CH2CI — C02(C2H5),  B.  Pt. 
145°,  and  ethyl  trichlor-acetate,  CCI3— C02(C2H5),  B.  Pt.  164% 


Isomers.     All  those   ethers   of  the  ^  diflferent  monatomic 


176 


VII.  ACID  DERIVATIVES. 


saturated  alcohols  and  acids  are  isomeric,  the  sums  of  whose 
carbon  atoms  are  equal  to  one  another ;  thus  methyl  butyrate 
is  isomeric  not  only  with  ethyl  propionate  but  also  with 
propyl  acetate  and  with  butyl  formate.  Further,  all  ethers 
are  isomeric  with  the  monobasic  acids  which  contain  an  equal 
number  of  carbon  atoms  with  them,  e.g.  the  ethers  just  men- 
tioned are  isomeric  with  valeric  acid.  (See  Metamerism, 
p.  93.) 

Further  cases  of  isomerism  occur  when  the  alcohol  on  the 
one  hand,  or  the  acid  on  the  other,  is  unsaturated,  e.g.  allyl 
propionate  and  propyl  aery  late. 


B.  Chlorides  of  the  Acid  Radicles. 

(Acid  Chlorides,  or  Chloro-anhydrides  of  the  Acids.) 

Among  the  halogen  compounds  of  the  acid  radicles  those  of 
chlorine  are  the  most  important. 

Formation.  (1)  From  the  acid  and  hydrochloric  acid  by 
means  of  phosphoric  anhydride ;  this  method  is  of  theoretical 
value  only  : 

C2H3O.OH  +  HCI  =  C2H3O.CI  +  H2O. 

(2)  By  the  action  of  chlorine  upon  the  aldehydes  ; 

CH3.OHO  +  CI2  =  CH3.COCI  +  HCI. 

(3)  By  the  action  of  the  chlorides  of  phosphorus,  PCI3  and 
PCI5,  upon  the  acids  or  their  salts : 

C^H^aOH  +  PClg  =  C4H^O.Cl  +  POCl3  +  HCl. 

The  acid  chloride  is  separated  from  the  POCI3  formed  at  the 
same  time  by  fractional  distillation.  In  the  case  of  acetic  acid 
PCI3  is  conveniently  used,  being  warmed  with  the  free  acid 
upon  the  water-bath : 

3C2H3O.OH  +  PCI3  =  3C2H3O.CI  +  PO3H3. 

Phosphorus  oxychloride,  POCI3,  may  also  be  allowed  to  act  upon  the 
alkaline  salts  of  the  acids  ;  when  the  latter  are  present  in  excess,  acid 
anhydrides  are  produced  (p,  178). 


ACID  CHLORIDES. 


177 


(4)  Several  of  the  acid  bromides  result  from  the  bromo-derivatives  of 
the  olefines  by  the  absorption  of  oxygen  from  the  air,  thus  CBr2=CH2 
yields  CHgBr — COBr,  bromo-acetyl  bromide. 

(5)  From  Phosgene,  COCI2,  and  zinc  alkyl  (see  p.  150). 

Properties.  The  acid  chlorides  are  suffocating  liquids  which 
fume  in  the  air,  distil  without  decomposition,  and  are  recon- 
verted by  water  into  the  corresponding  acids  and  hydrochloric 
acid,  for  the  most  part  at  the  ordinary  temperature : 

C2H3O.CI  +  H2O  =  C2H3O.OH  +  HCI. 

They  react  with  alcohol  and  the  alcoholates  to  form  ethers, 
with  the  salts  of  the  acids  to  form  anhydrides,  and 
with  ammonia  to  form  amides.  Sodium  amalgam  reduces 
them  to  aldehydes  and  alcohols.  With  zinc  alkyl  they  yield 
ketones  or  tertiary  alcohols,  according  to  the  conditions  of  the 
experiment.    (Cf  pp.  139  and  77.) 

On  treatment  with  silver  cyanide,  the  cyanides  of  the  acid  radicles 
are  formed,  e.g.  Acetyl  cyanide,  CH3.CO.CN,  from  acetyl  chloride. 
These  are  of  great  importance  for  the  synthesis  of  the  ketonic  acids, 
being  saponified  by  concentrated  hydrochloric  acid  in  the  same  way  as 
the  cyanides  of  the  alcohol  radicles,  with  transformation  of  —  CN  into 
— CO. OH;  dilute  hydrochloric  acid,  on  the  contrary,  decomposes  them 
into  the  original  acid  and  HON.  When  it  is  attempted  to  isolate  the 
acid  radicle  by  removing  the  halogen,  it  is  found  that  two  radicles  unite 
together  with  formation  of  double  ketones,  R — CO — CO — R,  compounds 
as  yet  but  slightly  investigated  (see  p.  221). 


Acetyl  chloride,  CH3.COCI.  Mobile  colourless  liquid  of 
suffocating  odour.  B.  Pt.  55°  ;  Sp.  Gr.  at  0°,  1*13.  Decom- 
poses violently  with  water,  with  ebullition,  and  with  strong 
ammonia  with  explosive  rapidity.  Is  a  reagent  of  exceptional 
importance,  since  it  serves  for  the  conversion  of  the  alcohols 
and  ammonia  compounds  (primary  and  secondary  amines)  into 
their  acetic  derivatives,  and  thus  frequently  leads  to  the 
explanation  of  the  chemical  nature  of  the  substance  under 
investigation. 

Among  the  homologues  of  acetyl  chloride  which  are  known  are 
Propionyl  chloride,   CgHg.COCl,  Butyryl  chloride,  G^H^.COCl,  Iso- 
valeryl  chloride,  C4Hy.C0Cl,  and  Palmityl  chloride,  CjglrLji.COCl ; 
(606)  M 


178 


VII.  ACID  DERIVATIVES. 


likewise  Acetyl  bromide,  CHg.COBr,  B.  Pt.  81°,  and  Acetyl  iodide, 
CH3.COI,  (from  iodine,  phosphorus  and  acetic  anhydride).  The 
chloride  of  formic  acid,  HCOCl,  is  however  unknown,  since  it 
immediately  breaks  up  into  CO  and  HCl  when  its  preparation  is 
attempted.  As  examples  of  chlorides  of  substituted  acids  we  may  take 
Mono-chlor-acetyl  chloride,  CH2CI.COCI,  B.  Pt.  106°,  and  Lactyl 
chloride,  CH3— CHCl— COCl. 


0.  Acid  Anhydrides. 

Corresponding  to  the  monobasic  fatty  acids  there  are 
anhydrides,  which  are  derived  from  two  molecules  of  the  acid 
with  the  separation  of  a  molecule  of  water,  e,g,  : 

CH3.CO.OH  _  CH3— CO^p.  xrn 
CH3.CO.OH   -   CH3— C0>^  ^2^- 

They  may  also  be  considered  as  oxides  of  the  acid  radicles, 
for  instance,  (C2H30)20,  =  Acetyl  oxide. 

Preparation.  1.  They  do  not  as  a  rule  result  from  the  acids 
by  direct  abstraction  of  water,  but,  e.g.^  by  the  action  of  acid 
chlorides  upon  the  alkaline  salts  of  the  acids  : 

C2H30Cl  +  C2H30.0Na  =  ^2^30^0  + NaCl. 

P.  By  the  direct  action  of  phosphorus  oxychloride  upon 
the  alkaline  salts  of  the  acids,  acid  chlorides  being  formed  in 
the  first  instance,  (see  p.  176). 

2.  By  the  action  of  phosgene  on  the  acids,  (B.  17,  1286) : 

2CH3.CO.OH  +  COCI2  =  (CH3— 00)^0  +  CO2  +  2HCL 

2'^.  The  anhydrides  of  the  higher  acids  are  conveniently 
prepared  by  treating  these  with  acetyl  chloride,  (B.  10, 
1881) : 

2R.C0.0H  +  CH3.COCI  =  (R.C0)20  +  CH3.COOH  +  HCl. 

Properties.  The  most  of  the  acid  anhydrides  are  liquids, 
but  those  of  higher  molecular  weight  solids,  of  neutral  re- 
action and  soluble  in  alcohol  and  ether.  They  are  insoluble  in 
water,  but  are  gradually  decomposed  by  it  into  acid  hydrates. 
On  warming  with  alcohol,  compound  ethers  are  formed,  and  by 


ACID  ANHYDRIDES;   THIO-ACIDS.  179 

tlie  action  of  ammonia,  amides.  They  yield  with  HCl  gas,  acid 
chloride  and  free  acid  : 

(C2HaO)20  +  HCl  -  C,H30.C1  +  C2H30.0R 


Acetic  anhydride,  (021130)20,  is  a  mobile  liquid  of  suffocat- 
ing odour,  boiling  at  137°,  and  having  a  Sp.  Gr.  at  20°  of  1*073. 
Like  acetyl  chloride  it  is  a  reagent  of  great  importance,  since 
it  converts  primary  and  secondary  ammonia  derivatives  into 
acetyl  compounds. 

Intermediate  or  Mixed  anhydrides  containing  two  different  acid 

CHOI 

radicles  are  also  known,  {Gerhardt,  Williamson),  e.g.  q^jj^  0/^'  ^^^y 
break  up  into  two  simple  anhydrides  upon  distillation. 

We  are  likewise  acquainted  with  peroxides  of  the  acid  radicles,  e.g. 
Acetyl  peroxide,  (C2H30)202,  a  thick  liquid  insoluble  in  water,  which 
acts  as  a  strong  oxidizing  agent  and  explodes  upon  warming  ;  it  is  pre- 
pared by  the  action  of  barium  peroxide,  BaOg,  upon  acetic  anhydride. 

D.  Thio-acids  and  Thio-anhydrides. 

Just  as  in  the  alcohols  and  ethers,  so  in  the  acids  and  their 
Anhydrides  is  oxygen  replaceable  by  sulphur.  There  are  thus 
theoretically  possible :  (1)  Thio-acids,  e.g.  thiacetic  acid, 
CH3.CO.SH,  and  their  isomers,  e.g.  CH3.CS.OH,  (as  yet 
unknown);  (2)  Thio-anhydrides,  e.g.  acetyl  sulphide,  (021130)28; 
(3)  Di-thio-acids,  e.g,  CH3CS.SH,  (as  yet  only  known  in  the 
aromatic  series). 


Thiacetic  acid,  C2H3O.SH,  is  a  colourless  liquid  boiling 
below  100°,  which  smells  of  acetic  acid  and  sulphuretted 
hydrogen,  and  readily  decomposes  with  water  into  those  two 
components.  It  is  prepared  from  acetic  acid  and  phosphorus 
pentasulphide,  P2S5.  The  other  thio-compounds  are  likewise 
easily  saponifiable,  with  formation  of  acetic  and  hydrosulphuric 
acids. 


180 


VII.  ACID  DERIVATIVES. 


Ethers  of  tliiacetic  acid  are  also  known,  e.g.  ethyl  thiacetate, 
CH3CO.S.C2H5,  which  is  obtained  from  acetyl  chloride  and  sodium 
mercaptide  ;  they  are  liquids  which  distil  without  decomposition,  and 
are  easily  saponified  back  to  acid  and  mercaptan. 


E.  Amides. 

By  the  replacement  of  the  hydrogen  in  ammonia  by  acid 
radicles  or,  in  other  words,  by  the  replacement  of  the  acid 
hydroxyl  by  amidogen,  etc.,  amides  result,  these  being 
primary,  secondary,  or  tertiary,  according  to  the  number  of 
hydrogen-atoms  substituted ; 

NH,.C,H30       NH(C2H30),  N(C2H30)3. 

 ^  ^  ^-  Y   ^   y  

Acetamide.  Di-acetamide.  Tri-acetamide. 

Of  these  the  primary  amides  are  the  most  important.  They 
are  solid  crystalline  compounds,  at  first  soluble  in  water  but 
becoming  insoluble  with  increasing  carbon,  and  soluble  in 
alcohol  and  ether.  They  distil  without  decomposition,  when 
necessary,  in  a  vacuum.  They  differ  characteristically  from 
the  amines  in  being  easily  saponifiable,  breaking  up  into  their 
components,  acid  and  ammonia,  when  super-heated  with  water 
or  when  boiled  with  alkalies  or  acids. 

Alkylated  amides  are  compounds  derived  from  ammonia  by  the 
replacement  of  its  hydrogen  by  alcoholic  and  acid  radicles  at  the  same 
time,  e.g.  ethyl  acetamide,  C2H30.NH.(C2Hg)  and  di-methyl  aceta- 
mide, (CHgjgN.CgHgO.  They  are  to  be  regarded  as  acid,  e.g.,  acetyl- 
derivatives  of  the  nitrogen  bases  of  alcohol  radicles  ;  thus,  ethyl  aceta- 
mide is  the  same  as  acetyl  ethylamine,  C2Hg.NH(C2H30). 

Modes  of  formation.  1.  By  the  dry  distillation  of  the 
ammonium  salts  of  the  fatty  acids  or,  better,  by  heating  them 
in  a  closed  vessel  to  230°  (Hofmann,  B.  15,  977),  thus : 

CH3CO.ONH4  =  CH3OO.NH2  +  H2O. 

2.  By  addition  of  water  to  the  cyanides  of  the  alcohol 
radicles  containing  one  atom  of  carbon  less  than  them- 
selves : 

CH3— ON  +  Hp  -  CH3— CO.NHg. 


AMIDES. 


181 


This  assimilation  of  water  is  frequently  effected  by  dissolv- 
ing the  nitrile  in  concentrated  sulphuric  acid,  or  in  acetic  and 
concentrated  sulphuric  acids,  or  by  shaking  with  concentrated 
hydrochloric  acid  in  the  cold;  also,  and  often  quantitatively, 
by  hydrogen  peroxide,  HgOg. 

3.  By  the  action  of  acid  chlorides  upon  aqueous  ammonia  or 
solid  ammonium  carbonate : 

CH3.COCI  +  2NH3  =  CH3.CONH2  +  NH4CI. 
3*.  In  an  analogous  manner  from  acid  anliydrides  : 

(C2H30)20  +  2NH3  =  C2H3O.NH2  +  C2H3O.ONH4. 

4.  By  heating  compound  ethers  with  ammonia,  sometimes 
even  on  shaking  in  the  cold  : 

CH3.CO.OC2H5  +  NH3  =  CH3,CONH2  +  C2H5OH. 

5.  The  secondary  and  tertiary  amines  result  upon  heating 
the  acids  or  anhydrides  with  their  nitriles  : 

CH3.CN  +  CH3.COOH   -  (CH3.C0)NH; 
CH3.CN  +  (CH3.CO)20  =  (CH3.CO)3N. 

Behaviour,  1.  The  amides,  although  derivatives  of  ammonia, 
are  hardly  basic,  the  strongly  positive  character  of  the 
hydrogen  atoms  of  the  ammonia  being  cancelled  by  the 
entrance  of  the  negative  acid  radicle.  Still  the  primary 
amides  are  capable  of  forming  addition-compounds  with  some 
acids,  e.g.  acetamide  yields  the  compound  (C2H30.NH2)2HC1, 
"  acetamide  hydrochloride  "  ;  these  are  however  unstable,  and 
are  decomposed  for  the  most  part  by  water  alone.  On  the 
other  hand  the  hydrogen  of  the  amido-group  can  be  replaced 
by  particular  metals,  especially  mercury,  the  amides  therefore 
playing  the  role  of  weak  acids  in  the  compounds  so  obtained^ 
e.g.  mercury  acetamide,  (CH3.CONH)2Hg. 

2.  The  amides  are  readily  saponifiable.  When  they  also 
contain  alcoholic  radicles,  only  the  acid  and  not  the  alcohol 
radicle  is  separated  on  saponification,  in  accordance  with  the 
fact  that  the  amine  bases  are  not  saponifiable,  thus  : 

C2H3O.NHC2H5  +  NaOH  =  CgHgO.ONa  +  CgH^NHg. 


182 


VII.   ACID  DERIVATIVES. 


3.  Nitrous  acid  converts  the  primary  amides  into  the  corre- 
sponding acids,  with  liberation  of  nitrogen  : 

C2H3O.NH2  +  NO2H  -  C2H3O.OH  +  N2  +  H2O. 
This  reaction  is  a  general  one,  and  corresponds  exactly  with 
the  action  of  nitrous  acid  upon  the  primary  amines. 

4.  Upon  heating  the  primary  amides  with  phosphorus 
pentoxide,  P2O5,  nitriles  are  produced  (see  p.  107).  These 
are  also  obtained  upon  heating  with  PgSg,  and  PCI5,  amido- 
chlorides  or  thiamides  being  in  this  case  formed  as  inter- 
mediate products,  (see  pp.  107  and  184). 

5.  If  bromine  in  the  presence  of  alkali  is  allowed  to  act 
upon  primary  amides,  there  ensue  in  the  first  instance 
amides  whose  NH2-hydrogen  is  replaced  by  halogen,  e.g. 
CH3.CO.NHBr,  aceto-bromamide,  (colourless  rectangular 
plates),  and  CH3.CO.NBr2 : 

CH3— CO.NH2  +  Brg  =  CH3— CO.NHBr  -h  HBr,  etc. 

These  yield  peculiar  urea  derivatives  with  more  amide 

and  alkali,  e.g.  methyl-acetyl-urea,  CO  |  ^jj  Qg^^^j  which 

are  split  up  by  further  addition  of  alkali  in  the  normal  manner, 
with  formation  of  amines — in  this  case  CH3.NH2 — containing 
one  atom  of  carbon  less  than  the  original  product.  (See  urea.) 
This  is  an  excellent  method  for  preparing  the  amines  from  C^ 
to  Cg,  but  less  desirable  for  those  from  Cg  onwards,  as  in  the 
case  of  the  higher  molecular  compounds  the  production  of  amine 
diminishes,  a  nitrile  being  formed  instead  by  the  further 
action  of  the  bromine,  (see  below).  Such  nitriles  C?^,  in  which 
71  >  5,  can  therefore  be  obtained  directly  from  the  amine  by 
the  action  of  bromine  and  alkali  upon  it,  thus  : 

C.H15— CH2.NH2  +  2Br2  =  C.Hi,— CH2.NBr,  +  2HBr 
=  C^Hi,.CN  +  4HBr. 

(Eeversal  of  the  Mendius  reaction,  p.  113;  cf.  Hofmann,  B.  15, 
407,  752;  17,  1407,  1920;  18,  2737). 

Since  these  nitriles  go  on  saponification  into  acids  containing 
one  atom  of  carbon  less  than  the  amide  originally  taken,  this 
reaction  renders  it  possible  to  descend  in  the  series  successively 


AMIDO-  AND  IMTD0-CI1L0R[])K{H. 


183 


tVom  one  acid  to  another,  (p.  145).  This  has  been  done  in  the 
case  of  the  normal  acids  from  C^^  to  C^,  and  constitutes  a 
further  proof  of  their  normal  constitution. 


Form  amide,  HCO.NH2,  is  a  liquid  readily  soluble  in  water 
and  alcohol,  which  boils  with  partial  decomposition  at  about 
200°,  and  breaks  up  into  CO  and  NH3  when  quickly  heated. 
It  yields  hydrocyanic  acid  when  heated  with  P2O5. 

Acetamide,  CgHgO.NHg.  Long  needles,  readily  soluble  in 
water  and  alcohol.    M.  Pt.  82°,  B.  Pt.  222°. 

The  high  boiling  points  of  the  amides  are  worthy  of  notice ;  they 
stand  in  striking  contrast  to  the  low  boiling  points  of  the  amines  con- 
taining an  equal  amount  of  carbon. 

Among  the  amides  of  haloid-substitution  acids  may  be  mentioned  : 

Mono-chlor-acetamide,  CHgCl— CO.NHg,  M.  Pt.  116°,  B.  Pt.  225°. 

Tri-chlor-acetamide,  CCI3— CO.NHg,  M.  Pt.  136°,  B.  Pt.  239°. 

For  Isomers  of  the  Amides,  see  p.  185. 

F.  Amido-chlorides  and  Imido-chlorides. 

By  the  action  of  PCI5  upon  the  primary  amides,  an  exchange 
of  CI2  for  0  takes  place,  giving  rise  in  the  first  instance 
to  the  so-called  amido-chlorides,  e.g,  acet-amido  chloride, 
CH3 — CClg.NHg;  these  are  extremely  easily  decomposable 
compounds,  being  reconverted  by  water  into  amide  and  hydro- 
chloric acid,  and  readily  giving  up  HCl,  with  formation  of 
imido-chlorides,  e.g.  CH3 — CCl  :  NH,  acet-imido  chloride. 
The  imido-chlorides  also  decompose  easily  as  a  rule,  likewise 
yielding  with  water  the  amide  and  hydrochloric  acid.  When 
heated,  they  break  up  into  nitrile  and  hydrochloric  acid. 

The  alkylated  amides  (p.  180)  also  yield  amido-chlorides,  e.g. 
CH3.CO.NH.C2H5  gives  CH3.CCI2.NH.C2H5,  ethyl  acet-amido  chloride, 
and  CH3— CO.NR2  gives  CH3—CCI2.NR2;  if  these  still  contain 
amido-hydrogen,  they  likewise  go  readily  into  imido-chlorides,  e.g* 
CH3.CC1=N.C2H5,  ethyl  acet-imido  chloride. 

The  chlorine  in  these  compounds  is  very  active,  chemically; 
it  can  be  exchanged  for  sulphur  or  for  an  ammonia  (amine-) 


184 


VII.   ACID  DERIVATIVES, 


residue  by  the  action  of  sulphuretted  hydrogen,  ammonia,  or 
amine,  with  the  formation  of  thiamides  and  amidines,  thus  : 

CH3.CCI2.NHR  f  H^S  -  CH3.CS.NHR  +  2HC1. 
CH3.CCI :  NR  +  NH3    =  CH3.C(NH2)  :  NR,  etc. 

Most  of  the  amido-  and  imido-chlorides  known,  (0.  Wallach,  1S75), 
contain  aromatic  radicles,  e.g.  CgHg,  phenyl,  and  the  same  remark  also 
applies  to  the  following  classes  of  compounds. 

G.  Thiamides  and  Imido-thio-ethers. 

Thiamides  are  compounds  derived  from  the  amides  by  the 
exchange  of  oxygen  for  sulphur,  e.g.  CHg.CS.NHg,  aceto- 
thi amide  or  thiacetamide,  CHg.CS.NHCgH^,  thiacetanilide. 
They  are  mostly  crystalline  compounds,  and  result  from  the 
addition  of        to  the  nitriles,  (CaJiours),  e.g,  : 

CH3.CN  +  H^S  =  CH3.CS.NH2; 

by  treating  acid  amides  with  P2S5 ;  from  the  amido-  etc. 
chlorides,  as  given  above ;  and  by  the  action  of  H2S  or  CS2 
upon  the  amidines.  Both  simple  and  alkylated  thiamides  are 
known. 

The  thiamides,  R — CS.NHg,  break  up  upon  heating  into 
nitrile  and  sulphuretted  hydrogen,  (see  p.  107).  They  are  all 
easily  saponified  by  alkalies,  etc.,  with  formation  of  the  corre- 
sponding acid,  ammonia  (amine)  and  H2S,  thus : 

E— CS.NHR  +  2H2O  -  R— CO.OH  +  H2S  +  NH2.R. 

They  are  rather  more  acid  in  character  than  the  amides,  and 
thus  many  of  them  are  soluble  in  alkali  and  yield  metallic 
derivatives. 

The  alkylated  thiamides  of  formic  acid  also  result  from  the 
addition  of  hydrogen  sulphide  to  the  iso-nitriles : 

CN.R  +  H2S  =  H— CS.NHR. 

SH 

From  the  compound  CH3— C^-^jj,  isomeric  with  thiacetamide,  and 

which  one  might  term  acetimido-thio-hydrate,  or  iso-thiacetamide,  but 
which  is  not  known  in  the  free  state,  there  are  derived  a  number 
of  compounds,   the  Imido-thio-etherSf   by  the  replacement  of  the 


IMIDO-THIO-ETHKRS  ;  AMIDINES.  185 

sulphydril,  and  also  of  the  iinido-,  hydrogen  by  an  alcohol  radicle,  e.g. 
acetimido-thio-ethyl,    CH3— C^^j^  ^;    methyl  iso- thio-acetanilide, 

CH3 — C^^^^  .    They  are  decomposed  by  hydrochloric  acid  into 

ethers  of  thiacetic  acid,  thus  : 

CH3— C(NH).S.CH3  +  H2O  =  CH3— CO.SCH3  +  NH3. 

These  imido-thio-ethers  are  prepared  by  the  action  of  mercaptans 
upon  nitriles  in  presence  of  hydrochloric  acid  gas  {Pinner),  and  by  the 
action  of  alkyl  iodides  upon  thiamides  (  Wallach,  Bernthsen) : 

^•C<NH,  +  =  R.C<g^H^  +  HI. 

Irnido- ethers f  R — C!^q^,  which  are  the  oxygen  compounds  corre- 
sponding to  the  above  imido-thio-ethers,  and  which  are  isomeric  with 
the  amides,  are  also  known,  {Pinner).     They  are  derived  from  the 

imido-hydrates  of  the  acids,  e.g.  from  acetimido  hydrate,  CH3— C^q^, 

hypothetical  compounds  unknown  in  the  free  state,  which  are  isomeric 
with  the  simple  amides.  The  imido-ethers  result  from  the  combination 
of  a  nitrile  with  an  alcohol  under  the  influence  of  hydrochloric  acid 
gas  ;  some  of  them  are  liquids  which  boil  without  decomposition,  but 
others  are  only  known  in  the  form  of  salts. 


H.  Amidines. 

Amidines  or  amimides  are  compounds  derived  from  the 
amides,  R— CO.NH^,  RCO.NHR',  and  R— CO.NR'g,  by  the 
exchange  of  oxygen  for  the  imido-residue  NH  or  (NE)" : 

Acetamidine,  (ethenyl  amidine).    Ethenyl-diphenyl  amidine. 

The  amidines  are  well  characterized  and  partly  crystalline 
bases  which  often  form  stable  salts.  They  differ  however  from 
the  amines  in  that  they  are  easily  saponified,  a  property  which 
is  common  to  all  acid  derivatives. 

Formation.  (1)  By  heating  the  amides  with  amines  in 
presence  of  PCI3  (Bofmann) : 

R— CO.NHR'  +  NH^R'  =  R— C(NR')(NHR')  +  B.f>. 


186 


VII.  ACID  DERIVATIVES. 


(2)  By  treating  the  imido-chlorides,  thiamides  and  iso-thi- 
amides  with  ammonia  or  with  primary  or  secondary  amines 
( JFallach,  Bernthsen),  thus  : 

R_CS.NH2  +  NH^R'  =  R— C(NH)(NHR')  +  H^S ; 
R_C(NH)(SR)  +  NH3  =  R— C(NH)(NH2)  +  RSH. 

(3)  By  heating  the  nitriles  with  amine  hydrochlorate ;  this 
method  is  a  particularly  easy  one  when  aromatic  amines  are 
used,  but  not  in  the  case  of  chloride  of  ammonium  (Bernthsen) : 

CH3— CN  +  NH2.R  =  CH3— C(NH)(NHR). 

(4)  By  the  action  of  amine  bases  or  ammonia  upon  imido-ethers. 

Behaviour,  (1)  They  decompose  into  ammonia  or  amine  and 
acid  upon  boiling  with  acids  or  alkalies  (see  above),  and  into 
ammonia  and  amide  upon  boiling  with  water. 

(2)  In  the  dry  state  they  easily  break  up  on  heating  into 
ammonia  or  amine  and  acid  nitrile,  so  long  as  the  imido-hydro- 
gen  atom  has  not  been  replaced  by  alcoholic  radicle. 

(3)  Upon  heating  with  hydrogen  sulphide,  thiamides  are 
formed. 

In  this  reaction  combination  between  the  two  reagents  at  first 
occurs,  thus  : 

NH  /NHg 
R — C<rxrTT  -Q  +  HoS  =  R — Cr — SH 

^^•^  \nh.r' 

the  resulting  addition  product  then  breaking  up  in  two  directions,  viz. 
(a)  into  K— CS.NH2  +  NH2R,  and  {b)  into  R— CS.NHR  + NH3. 
Similar  intermediate  addition  compounds  must  be  assumed  in  corre- 
sponding reactions,  e.g.  in  the  conversion  of  imido-chlorides  into 
amides. 

(4)  Upon  being  heated  with  CS^,  the  amidines  also  yield  thiamides, 
sulphocyanic  acid  or  an  iso-thiocyanate  being  formed  at  the  same  time. 

Most  of  the  thiamides  which  have  been  prepared  belong  to  the  aro- 
matic group.    (See  A.  184,  129 ;  192,  1 ;  B.  12,  1061.) 


Amidoximes. 


As  amidoximes  are  designated  compounds  which  result  on  the  addi- 
tion of  hydroxylamine  to  nitriles,  and  which,  from  this  mode  of  formation 


POLYATOMIC  ALCOHOLS.  187 

and  from  their  properties,  appear  to  be  amidiiies  in  which  an  amido- 
(iiuido-)  hydrogen  atom  is  replaced  by  hydroxy  1  : 

R_CN  +  NH.OH  =  R_C<^g^^. 

Such  an  amidoxime  is,  for  instance,  Isuret,  H — ^^^^^^  ^  ^^^^ 
termed  methenyl  amidoxime,  isomeric  with  urea,  which  results  from 
hydrocyanic  acid  and  hydroxylamine ;  also  Ethenyl  amidoxime, 
CH3— C(N.0H)(NH2).  These  compounds  are  decomposed  by  saponi- 
fying agents  in  a  similar  way  to  the  amidines.    Related  to  them  are 

substances  of  the  constitution       C^^O 'CgHg'  hydroxamic  acids, 

e.g.  ethyl-benz-hydroxamic  acid,  R — ^i^^^J^^^.     (R^CeHg.)  (Cf. 

Tiemann,  B.  17,  129,  1685;  Lossen,  B.  17,  1587.) 

The  hydroxamic  acids  show  interesting  cases  of  isomerism.  {LosseUy 
A.  161,  347 ;  176,  271 ;  186,  1.) 


VIIL  POLYATOMIC  ALCOHOLS. 
A.  Diatomic  Alcohols  or  Glycols. 

C/nH2n+202,     =  CnH2n(OH)2. 

The  diatomic  alcohols  differ  from  the  monatomic  in  the 
same  way  as  the  di-acid  bases  do  from  the  mono-acid.  Just 
as  the  di-acid  bases  react  with  a  monobasic  acid  to  form 
neutral  and  basic  salts,  while  a  mono-acid  base  can  only  yield 
a  neutral  salt,  so  do  the  diatomic  alcohols  give  with  monobasic 
acids  two  series  of  ethers,  and  with  ammonia  two  kinds  of 
amines,  etc.  Of  these  compounds  the  members  of  the  one 
class  correspond  to  the  neutral  salts,  and  possess  in  full  degree 
the  character  of  ethers,  amines,  etc.,  while  the  members  of  the 
other  retain  their  alcoholic  character  and  correspond  in  com- 
position with  the  basic  salts  (which  still  retain  their  basic 
nature),  thus : 


Pb{OH  PbjOH  p,/Cl 


OH  CI    .  CI 


Lead  hydroxide.     Basic  lead  chloride.      Neutral  lead  chloride. 


188 


VIII.  POLYATOMIC  ALCOHOLS. 


Glycol. 


C2H4 


OH 
CI 


CI 
CI 


Glycol  chlorhydrin. 

pXT  fOH 
^2^*  1  O.C2H3O 


Glycol  dichlorhydrin. 

O.C,H,0 


o.cJhJo 


Glycollic  acetate. 

OH 

NH. 


C, 


Glycollic  di- acetate. 

NH, 


NH„ 


Hydroxy-ethylamine.        Ethylene  diamine. 

The  above  compounds  are  therefore  alcohols  similar  to  the  monatomic, 
and,  like  these,  they  give  rise  to  every  class  of  alcoholic  derivative. 
But  when,  for  example,  the  formation  of  an  ether  such  as  glycollic 
acetate  has  taken  place,  this  still  behaves  as  a  monatomic  alcohol, 
yielding,  e.g.  with  a  second  molecule  of  acid,  a  new  ether. 

It  is  not  necessary  that  both  the  groups  which  replace  the 
hydrogen  or  hydroxyl  should  be  of  the  same  nature ;  thus  we 

know  a  mixed  derivative  of  the  composition  C2H4<^gQ  |j, 

which  possesses  at  one  and  the  same  time  the  character  of  an 
amine  and  of  a  sulphonic  acid. 

The  glycols  are  mostly  thick  liquids  of  sweetish  taste,  being 
only  occasionally  solid  crystalline  compounds,  easily  soluble 
in  water  and  alcohol,  but  difficultly  soluble  in  ether.  Their 
boiling  points  are  much  higher  than  those  of  the  corresponding 
monatomic  alcohols,  just  as  these  latter  possess  considerably 
higher  boiling  points  than  the  hydrocarbons  from  which  they 
are  derived. 

Constitution.  Just  as  the  monatomic  alcohols  are  character- 
ized by  the  presence  of  a  hydroxyl  group  linked  to  a  hydro- 
carbon radicle,  so  in  the  diatomic  alcohols  two  such  hydroxyls 
must  be  assumed;  and,  as  we  look  upon  the  monatomic 
alcohols  as  oxy -hydrocarbons,  so  we  may  regard  the  diatomic 
alcohols  as  di-oxy-hydrocarbons,  i.e.  as  being  derived  from  the 
hydrocarbons  by  a  double  replacement  of  H  by  OH. 

Glycols  which  would  contain  two  hydroxyls  linked  to  the 
same  carbon  atom  are  incapable  of  existence,  and  are  only 


GLYCOLS  ;  CONSTITUTION  AND  FORMATION. 


189 


known  in  derivatives  (see  pp.  131  and  139).  All  glycols  con- 
tain their  hydroxyls  attached  to  two  different  carbon  atoms. 
Glycol  has  thus  the  constitution  CH2(0H) — CH2(0H),  which 
can  be  proved  directly  by  transforming  it,  by  means  of  hydro- 
chloric acid,  into  glycol  chlorhydrin,  CH2CI — CH2.OH,  and 
oxidizing  the  latter  to  mono-chloracetic  acid,  CH2CI — CO. OH. 
In  this  last  compound  the  chlorine  and  hydroxyl  are  bound  to 
different  carbon  atoms,  and  consequently  the  same  applies  to 
glycol  chlorhydrin  and  to  glycol.    (Of.  p.  67.) 

The  monatomic  alcohols  are  distinguished  as  primary, 
secondary,  and  tertiary.  The  glycols  may  in  the  same  way 
be  characterized  as  di-primary  when  they  contain  the  group 
CH2.OH  twice,  as  in  glycol;  as  primary-secondary  when  they 
contain  the  group  CHg.OH  together  with  the  group  CH.OH,  as 
in  propylene  glycol,  CH3 — CH(OH) — CHgOH  ;  further  as  di- 
secondary,  primary-tertiary,  secondary-tertiary,  and  di-tertiary. 
In  all  these  cases  the  behaviour  of  the  compound  upon  oxida- 
tion yields  an  explanation  of  its  nature.  (For  particulars, 
see  p.  205.) 

Modes  of  formation.  1.  From  the  di-bromo  substitution 
products  of  the  hydrocarbons,  e.g,  ethylene  bromide  : 

(a)  By  transformation  into  the  di-acetic  ether,  by  means  of 
silver  or  potassium  acetate,  and  saponification  of  the  ether  so 
produced  by  potash  or  baryta  water  : 

C£^+  1kgG,^f>,  =  C,H,(C,H30,),  +  2AgBr; 

Ethylene  bromide.  Glycollic  di-acetate. 

C,H,(C,H302)2  +  2K0H  =  C,H,(OH),  +  2G,^f),K. 
In  the  actual  preparation  of  glycol  from  ethylene  bromide, 
potassium  acetate  and  strong  alcohol  (Demole),  this  saponifica- 
tion ensues  directly  upon  prolonged  boiling  of  the  mixture. 

(b)  By  boiling  with  water  and  lead  oxide  or  potassium 
carbonate,  by  which  means  the  acid  produced  is  taken  up,  and 
so  the  reaction  is  facilitated  : 

C2H4Br2  +  2H0H  =  C2H4(OH)2  +  2HBr. 
2.  By  the  reduction  of  ketones  to  secondary  alcohols,  the  so-called 


190 


Vni.  POLYATOMIC  ALCOHOLS. 


pinacones,  i.e.  di-tertiary  glycols,  result  as  bye-products,  (see  pp.  77 
and  191),  thus  : 

(CH3),C0  +  CO(CH3)2  +       =  (CH3)2=C(OH)-C(OH)=(CH,)2. 


Pinacone. 

3.  By  the  combination  of  olefines  with  H2O2,  or  from  their 
oxidation  by  means  of  KMnO^,  the  glycols  are  produced 
directly,  and  by  their  combination  with  ClOH,  the  chlor- 
hydrins  : 

C2H4  +  ClOH  =  C^H^CKOH). 

Behaviour.  1.  As  in  the  case  of  the  monatomic  alcohols,  the 
hydrogen  is  directly  replaceable  by  potassium  or  sodium,  with 

the  formation  of  alcoholates,  e.g.  C^2H4<Co^a  ^^^^ONa' 
sodium  and  di-sodium  glycols. 

2.  The  metal  in  these  compounds  may  be  exchanged  for 
new  alcohol  radicle  by  treatment  with  alkyl  iodide,  with 
formation  of  glycollic  ethers  : 

C2H4(ONa)2  +  2C2H5I  =  2NaI  +  C,R,{O.C,IL,),. 

Ethylene  di-ethyl  ether. 
These  ethers,  like  those  of  the  monatomic  alcohols,  are 
stable  against  saponifying  agents. 

3.  Acids  act  upon  them  to  produce  ethers,  which  are  either 
neutral  ethers  or  ether-alcohols  (see  p.  188). 

The  halogen  ethers  of  the  glycols  are  termed  chlor-,  brom-,  or 
iodhydrins,  e.g.  glycol  chlorhydrin,  C2H4C1(0H),  glycol  di-chlorhydrin, 
C2H4CI2,  etc.  The  ether-alcohols  which  result  from  the  action  of 
halogen  hydride  may  also  be  regarded  as  mono-substitution  products 
of  the  monatomic  alcohols,  which  cannot  be  prepared  directly,  e.g. 
C2H4C1(0H),  monochlor-ethyl  alcohoL  Similarly  the  neutral  halogen 
hydride  ethers,  C2H4CI2,  C2H4Br2,  etc.,  are  nothing  else  than  the 
di-substitution  products  of  the  paraffins. 

4.  The  chlor-,  brom-,  and  iodhydrins,  as  the  chlorides, 
etc.  of  the  monatomic  alcohols,  constitute  the  bridge  for  the 
preparation  of  most  of  the  other  glycol  derivatives ;  thus  they 
yield  thio-glycols  with  potassium  hydrosulphide,  glycollic 
amines  with  ammonia,  glycollic  sulphonic  acids  with  bisulphite 
of  soda,  etc. 


GLYCOLS. 


191 


5.  By  the  splitting  off  of  HCl  from  ethylene  chlorhydrin 
by  means  of  alkali,  there  is  formed  an  anhydride  of  glycol, 


have  also  been  prepared. 

The  glycols  frequently  yield  aldehydes  or  ketones  by  giving  up 
water,  for  instance,  ethylene  glycol  is  converted  into  aldehyde  by 
warming  with  chloride  of  zinc,  or  with  water  to  230°.  This  reaction  is 
explained  by  assuming  the  intermediate  formation  of  unsaturated 
alcohols  which  are  not  in  themselves  capable  of  existence,  e.g. 
CH2  =  CH(0H),  but  which  immediately  undergo  transformation  into  the 
isomeric  aldehydes  or  ketones. 

7.  For  the  oxidation  products  of  glycol,  see  above,  also  p. 


Methylene-  and  Ethylidene  glycols.    See  Aldehydes. 

Ethylene  glycol,  glycol,  G^YlIo}1\,  {Wurtz,  A.  100,  110). 
Is  prepared  from  ethylene  bromide  by  means  of  potassium 
acetate  in  alcoholic  solution  (Demole),  or  of  potassium  carbonate 
in  aqueous  solution,  as  given  above,  (A.  192,  250).  For  pro- 
perties, see  above.  Its  formula  has  been  corroborated  by  the 
determination  of  its  vapour  density.  Oxidizing  agents  trans- 
form it  into  glycollic  and  oxalic  acids. 

Propylene  glycol  is  known  in  two  isomeric  forms,  viz.  : 

(a)  Tri-methylene  glycol  or  ^S-Propylene  glycol,  CH2(0H) — 
CHg — CHoOH,  which  is  prepared  from  tri-methylene  bromide, 
and  is  a  di-primary  glycol;  B.  Pt.  216°.  It  is  also  produced  by 
the  schizomycetes  fermentation  of  glycerine,  (B.  14,  2270). 


(b)  a-Propylene  glycol,  CH3— CH(OH)— CH2(0H),  can  be 


prepared  from  propylene  bromide  in  an  analogous  manner, 
but  is  most  easily  got  by  distilling  glycerine  with  caustic  soda. 
B.  Pt.  188°.  Becomes  optically  ( — )  active  on  fermentation, 
i.e.  fission  fungi  convert  it  into  two  active  modifications 
(  +  and  — ),  the  former  of  which  is  more  readily  attacked  by 
fermentation  than  the  latter. 

Four  Butylene  glycols,  and  various  Amylene-  and  Hexylene-  glycols, 
etc.,  are  also  known. 

Pinacone  or  Tetramethyl- ethylene  glycol,  (CH3)2=C(OH)— C(OH)  = 
(CHgjg.    For  formation,  see  p.  190.    Its  hydrate,  (  +  6H2O),  forms  large 


ethylene  oxide. 


homologues  of  which 


205. 


192 


VIII.  POLYATOMIC  ALCOHOLS. 


quadratic  tables ;  in  the  anhydrous  state  it  is  a  crystalline  mass  melting 
at  38°  and  boiling  at  178°.    When  warmed  with  dilute  sulphuric  acid  it 
yields  pinacoline,  CH3 — CO — C^(CH3)3,  (see  p.  144). 
Cocceryl  alcohol,  CgoHeoiOHjg.    In  cochineal  wax. 

Derivatives  of  the  Glycols. 

Ethyl   ethers.    Glycol  ethyl  ether,  03114^^  ^^jj^  and  Glycol 

di  ethyl  ether,  03114(0.02115)2,  are  liquids  of  pleasant  ethereal  odour, 
boiling  at  about  70°  lower  than  glycol. 

Acid  derivatives.  GlycoUic  acetate,  C2H4<^q'^     ^  and  Glycollic 

di-acetate,  03114(0.021130)2,  are  liquids  easily  soluble  in  water,  v/hich 
boil  at  a  slightly  lower  temperature  than  glycol.     The  former  is 
converted  by  gaseous   hydrochloric  acid  into  glycol  chlor-acetin, 
01 

02H4<^Q  OHO  ^^^^^  ^^^y  ^^^^  ^®  regarded  as  chlorinated  ethyl 
acetate. 

Glycol  chlorhydrin,  CgH^.Cl.OH,  is  obtained  by  passing 
hydrochloric  acid  gas  into  warm  glycol,  (B.  16,  1407),  or  by 
the  direct  combination  of  ethylene  and  hypochlorous  acid.  It 
is  a  liquid  miscible  with  water,  and  boiling  at  128°,  differing 
in  this  point  from  its  corresponding  alcohol  to  almost  the  same 
extent  as  ethyl  chloride  does  from  alcohol. 

Glycol  hromhydrin,  O2H4.Br.OH,  and  Glycol  iodhydrin,  C2H4.I.OH, 

are  analogous  compounds ;  the  last  named  decomposes  upon  distillation. 

OH 

Sulphuric  ethers  of  glycol,  e.g.  Glycol  suphuric  acid,  02H4<^q  SO.H 
also  exist.    The  latter  is  similar  to  ethyl-sulphuric  acid  in  its  behaviour. 

Glycollic  di-nitrate,  C2H4(N03)2,  is  prepared  by  acting  on 
glycol  with  sulphuric  and  nitric  acids  : 

02H4(OH)2  +  2NO2OH   =   C2H4(O.N02)2  +  2H2O. 

It  is  a  yellowish  liquid,  insoluble  in  water,  which  is 
saponified  by  alkalies  and  explodes  on  being  heated.  The 
formation  of  such  nitric  ethers  is  characteristic  of  the  poly- 
atomic alcohols,  (see  glycerine,  p.  201). 

By  treating  ethylene  bromide  with  potassium  cyanide, 
ethylene  cyanide,  C2H4(CN)2,  is  obtained.  It  is  crystalline, 
and  goes  into  succinic  acid,  C2^J^G02ii)2)  on  saponification, 


DERIVATIVES  OF  THE  GLYCOLS. 


193 


Avhence  it  may  be  termed  the  nitrile  of  this  acid.  Nascent 
hydrogen  transforms  it  into  butylene  diamine,  C4Hg(NH2)2, 
(see  p.  195).  Similarly  ethylene  chlorhydrin  is  converted  by 
potassium  cyanide  into  the  HCN-derivative  of  glycol, 

Ethylene  cyanhydrin,  CH2(0H)-— CH2.CN,  which  also 
possesses  the  properties  of  an  acid  nitrile,  (see  lactic  acid). 
Isomeric  with  it  is  ethylidene  cyanhydrin,  CHo.CH(OH) — CN, 
the  addition  product  of  hydrocyanic  acid  with  aldehyde, 
(p.  133). 

Acetone  cyanhydrin,  (CH3)2==C(OH)— CN,  see  p.  142. 

The  anhydride,  Ethylene  oxide,  C2H4O,  ( Wurtz),  is  obtained 
by  distilling  glycol  chlorhydrin  with  caustic  potash  solution. 
It  is  a  mobile  liquid  of  ethereal  odour,  mixing  and  gradually 
combining  with  water  to  ethylene  glycol.  B.  Pt.  13*5° ;  Sp. 
Gr.  <  1.  It  also  combines  with  acids  to  chlorhydrins  or 
mono-ethers  of  the  glycols,  this  affinity  for  acids  being  so 
strong  as  to  give  it  a  well  marked  basic  character,  which  is 
further  shown  by  its  precipitating  the  hydrates  of  the  heavy 
metals  from  solutions  of  their  salts.  It  is  isomeric  with 
aldehyde. 

Ethylene  oxide  combines  with  glycol  to  form  the  so-called  Poly- 
glycols,  e.g.  Di-ethylene  glycol,  C2H4(OH)— 0-C2H4(OH). 

Mercaptans  and  sulphides  of  the  glycol  series  also  exist,  e.g.  Glycol 
mercaptan,  C2H4(SH)2,  Ethylene  mono -thio -hydrate,  C2H4(OH)(SH),  and 
Di-ethylene  dl-sulphide,  (02114)282,  the  last  of  which  forms  a  sulph-oxide 
and  a  sulphone.  TMo-di-glycollic  chloride,  S(C2H4C1)2,  is  an  extremely 
poisonous  liquid. 

Amines  of  the  Diatomic  Alcohols. 

These  are  derived  from  glycol  by  the  replacement  of  one  or 
two  hydroxyl  groups  by  amidogen  : 


In  the  former  case  monatomic  (primary)  amines  containing 
oxygen  result,  compounds  which  retain  at  the  same  time  their 


Oxy-ethylamine. 


Ethylene  diamine. 


(506) 


N 


194 


VIII.  POLYATOMIC  ALCOHOLS. 


alcoholic  character;  in  the  latter,  diatomic  (primary)  bases  free 
from  oxygen,  the  diamines,  which  are  in  every  respect  analogous 
to  ethylamine.  These  compounds  may  also  of  course  be  held  as 
being  derived  from  one  or  two  molecules  of  ammonia  by  the 


exchange  of  H  for  (CgH^.OH),  "  oxy- ethyl,''  or  of  for 
(C2H4),  thus  : 


This  latter  view  permits  of  the  prediction  of  secondary  and 
tertiary  bases,  e.g,  • 


and  also  of  quartern ary  ammonium  bases,  of  such,  among 
others,  as  still  contain  monatomic  alcohol  radicles,  e.g,  : 


Such  bases  actually  exist,  and  show,  according  to  their  con- 
stitution, the  behaviour  of  primary,  secondary,  etc.,  amines  or 
ammonium  bases.  Ethylene  diamine,  for  instance,  can  react 
not  only  with  ethylene  bromide,  but  also  with  the  halogen 
compounds  of  the  monatomic  alcohol  radicles. 

The  bases  containing  oxygen,  such  as  oxy-ethylamine,  etc., 
are  termed  Oxy-alkyl-bases  or  Hydramines. 

If  two  hydrogen  atoms  in  a  molecule  of  ammonia  are  replaced  by  a 
divalent  alcohol  radicle,  *'Imines,"  e.g.  ethylene  imine,  (C2H4)NH", 
result. 

Their  Modes  of  formation  are  likewise  for  the  most  part 
analogous  to  those  of  the  monatomic  alcohol  bases,  viz.  : 

(1)  By  heating  ethylene  bromide,  etc.,  with  alcoholic  am- 
monia to  100°,  {Hofmann). 


and  N(C2H4.0H)3 
and  N2(C,H,)"3; 


N<^  (C^H^.OH),  Choline. 


AMINES  OF  THE  GLYCOLS. 


195 


The  primary,  secondary  and  tertiary  bases,  which  are 
formed  simultaneously,  can  be  separated  by  fractional  dis- 
tillation. 

The  oxy-alkyl  bases  are  obtained  in  an  analogous  manner  by 
using  ethylene  chlorhydrin,  thus  : 

C2H4(0H)C1  +  NH3  =  C2H4(OH)(NH2)  +  HCl. 

In  this  case  also  primary,  secondary  and  tertiary  bases  are 
produced  at  the  same  time,  and  are  separated  by  the  fractional 
crystallization  either  of  their.  HCl  salts  or  of  their  double 
platinum  chlorides. 

Ethylene  chlorhydrin  yields  choline  hydrochlorate  with  tri- 
methylamine. 

(2)  Primary  diamines  result  from  the  reduction  of  the 
nitriles,  CnH2n(CN)2,  which  is  best  effected  by  metallic  sodium 
in  the  hot  alcoholic  solution  : 

G£J^,  +  m,  =  02H,(0H2.NH2)2,  =  C,H3(NH,)2 

Ethylene  cyanide.  Butylene  diamine. 

(3)  Hydramines  ensue  by  the  direct  combination  of  ammonia 
with  1,  2,  or  3  molecules  of  ethylene  oxide  {Wurtz),  thus : 

C2H4O  +  NH3  =  C2H4(OH)(NH2). 

Ethylene  oxide,  tri-methylamine  and  water,  combine  to 
choline : 

C2H,0  +  H20  +  N(CH3)3  =  C2H,(OH)[N(CH3)3.0H]. 

Ethylene   diamine,   C2H4(NH2)2,  Di-ethylene  diamine, 

(C2H4)2N2H2,  etc.,  are  colourless  liquids  distilling  without 
decomposition,  the  former  boiling  at  123°,  and  having  an 
ammoniacal  odour. 

Tri-methylene  diamine,  C3Hg(NH2)2,  (see  B.  17,  1789); 
Butylene  diamine  (Tetra-methylene  di-amine),  C4Hg(NH2)2, 
(see  above;  also  p.  193). 

Penta-methylene  diamine,   C5Hio(NH2)2,  = 
CH2(NH2)— (CH2)3— CH2(NH2),  is  formed  by  the  reduction 
of  tri-methylene  cyanide,  CN — (0112)3 — ON,  which  on  its  part 
is  prepared  from  tri-methylene  bromide,  CHgBr — CHg — CHgBr 
and  KCN,  (Ladenburg), 


196 


VIII.  POLYATOMIC  ALCOHOLS. 


It  is  a  colourless  syrupy  liquid  of  very  pronouncexl  sper- 
maceti and  piperidine  odour,  which  solidifies  in  the  cold,  and 
boils  at  178°-I79°.  It  possesses  especial  interest  from  its 
giving  up  ammonia  and  yielding  piperidine,  CgH^^N,  syn- 
thetically. 

Oxy-ethylamine  and  the  other  hydramines  are  colourless  bases  which 
decompose  on  distillation. 

To  hydramines  of  the  constitution  (C2H5)2N — CHg — CHgOH,  etc., 
Ladenhnrg  gives  the  name  of  Alkines,  the  above  formula  indicating 
Tri-ethyl  alkine ;  and  the  ethers  which  they,  as  alcohols,  yield  with 
acids,  he  terms  Alkeines.    (B.  14,  2406  ;  15,  1143.) 

Choline,  bilineurine,  trimethyl-oxy ethyl  ammonium  hydroxide, 

N(CH3)3.(0,H,.OH)(OH)  or  0,H,<gH  ^^^^^^  (Streclcer). 

Is  found  in  the  bile  (x^^Vi  bile),  brain,  yolk  of  egg,  etc.,  being 
present  in  these  combined  with  fatty  acids  and  glycerine- 
phosphoric  acid  as  lecithine.  It  is  also  found  in  herring  brine, 
hops,  beer,  and  in  many  fungi,  etc.,  and  is  obtained  by  boiling 
sinapine  with  alkalies,  Sincaline ").  Choline  is  a  strong 
base,  difficultly  crystallizable,  deliquescent,  and  absorbing  car- 
bonic acid  from  the  air  with  avidity.  It  is  not  poisonous. 
The  HCl  salt  has  the  formula  N(CH3)3(C2H40H)C1,  and  the 
platinum  double  salt  crystallizes  in  reddish  yellow  plates. 

By  transforming  choline,  by  means  of  hydriodic  acid,  into 
its  iodide,  N(CH3)3(C2H4l)I,  and  treating  the  latter  with  moist 
oxide  of  silver,  and  also  from  the  putrefaction  of  choline,  there 
results 

Neurine  {vevpov,  nerve),  trimethyl-vinyl  ammonium  hydroxide, 
N(CH3)3(C2H3)OH  ( Hofmann).  This  base,  containing  the  un- 
saturated radicle  "  vinyl,"  C2H3,  is  very  similar  to  choline,  and 
can  also  be  prepared  from  brain  substance ;  it  is  only  known 
in  solution,  and  is  very  poisonous.  It  is  possibly  identical 
with  an  alkaloid  produced  in  dead  bodies  by  the  decay  of 
albuminous  matter.    It  can  be  re-transformed  into  choline. 

Sulphuric  and  Sulphurous  Acid  Derivatives  of  Glycol. 

Methylene  di-sulphonic  acid,  methionic  acid,  CH2=(S03H)2  :  needles. 
Oxy-methyl-sulplionic  acid,  CH2(OH)S03H :  difficultly  crystallizable. 
Ethylene  di-sulphonic  acid,  03114(80311)2 :  a  thick  liquid. 


ISETHIONIC  ACIB;  TAURINE. 


197 


Oxy-ethyl-sulphonicorisethionicacid,CH.^(OH)-CH5^(S03H), 
and  Ethionic  acid,  CHo(OSO,H)— CH,(Sd,H).  By  treating 
alcohol  with  sulphuric  anhydride,  or  by  the  direct  combination 
of  the  latter  with  ethylene,  Carbyl  sulphate,  CgH^SgOg,  the 
anhydride  of  ethionic  acid,  is  formed.  It  is  crystalline  and 
hygroscopic,  combining  immediately  with  water  to  ethionic 
acid.  The  latter  is  easily  converted  into  sulphuric  and  is- 
ethionic  acids  upon  boiling  with  water.  Isethionic  acid  is 
isomeric  with  ethyl-sulphuric,  but  differs  from  it  sharply  in  not 
being  saponifiable.  It  is  also  produced  by  the  oxidation  of 
ethylene  thio-hydrate,  CH2(OH).CH2SE[,  by  nitric  acid,  and 
by  heating  ethylene  chlorhydrin  with  K2SO3 ;  it  is  therefore  a 
sulphonic  acid  (see  p.  105). 

Ethionic  acid  is  a  sulphuric  ether  of  isethionic  acid,  in  which  the 
latter  acts  as  an  alcohol,  corresponding  with  the  constitutional  formula : 
CH2(0.  SO3H)— CHalSOgH). 

Isethionic  acid  is  a  thick  liquid  which  may  solidify  to  a 
stellate  crystalline  mass,  and  forms  stable  salts  and  also  an  ethyl 
ether,  etc.  It  yields  with  PCI5  the  chloride  CgH^.Cl— SOg.Cl, 
which  decomposes  with  water  to  Chloro-ethyl-sulphonic  acid, 
CHgCl — CH2(S03H).  This  latter  reacts  with  ammonia  (Kolbe) 
to  form 

Taurine,  CgH^NSOg  (Gmelin),  which  is  present  in  combina- 
tion with  cholic  acid  as  taurocholic  acid  in  the  bile  of  oxen  and 
many  other  animals,  also  in  the  kidneys,  lungs,  etc.  It  crystal- 
lizes in  large  monoclinic  prisms,  is  easily  soluble  in  hot  water 
but  insoluble  in  alcohol,  and  decomposes  upon  being  strongly 
heated.  From  the  above  mode  of  formation,  it  has  the  con- 
CH2.NH2 

stitution   I  =  Amido-ethyl-sulphonic  acid,  and  in 

CH2.SO3II 

accordance  with  this  constitution  it  unites  in  itself  the  pro- 
perties of  an  alcoholic  amine  and  a  sulphonic  acid,  and  is 
therefore  at  the  same  time  a  base  and  an  acid.  It  forms 
unstable  salts  with  alkalies,  but  not  with  acids,  the  groups 
NH2  and  SO3H  in  the  molecule  practically  neutralizing  one 
another,  so  that  its  reaction  is  neutral.    Nitrous  acid  converts 


198 


VIII.  POLYATOMIC  ALCOHOLS. 


it  into  isethionic  acid,  a  reaction  analogous  to  the  decom- 
position of  the  primary  amines  by  this  reagent.  As  the  sul- 
phonic  acid  of  an  alcohol,  it  is  not  changed  by  boiling  with 
alkalies  and  acids. 


The  constitutional  formulae  of  (the  secondary)  Di-ethylene-diamine, 

N"2H2(C2H4)2,  is  C2H4<^^jj^C2H4,  i.e.  it  is  a  compound  in  which  one 

has  to  assume  a  so-called  ''closed  chain"  or  "ring-shaped  atomic  com- 
bination."   (Cf.  benzene,  pyridine,  pyrrol,  etc.) 

B.  Triatomic  Alcohols. 

Those  alcohols  are  triatomic  which  are  capable  of  forming 
three  series  of  ethers  with  a  monobasic  acid,  in  such  manner 
that  the  production  of  the  neutral  ether  requires  three  mole- 
cules of  the  acid.  Three  hydroxyls  must  be  assumed  in  them, 
so  that  their  chemical  behaviour  depends  upon  whether  one  or 
two  or  all  three  of  these  are  brought  into  reaction,  with  the 
formation  of  simple  and  compound  ethers,  amines,  etc. 

Thus  there  exist,  for  instance,  the  following  three  glycerine 
ethers  of  acetic  acid  : 

^3^5  {  a^HgO     ^^Hs  {  ^aC.Ufi),  C3H,(O.C2H30)3. 

Mono-acetin.  Di-acetin.  Tri-acetin. 

Compounds  are  also  known,  as  in  the  case  of  the  diatomic 
alcohols,  which  contain  several  different  substituents  in  the 
place  of  the  hydroxyl. 

The  triatomic  alcohols  are  colourless  thick  liquids  of  sweet 
taste  and  high  boiling  point,  and  are  for  the  most  part  easily 
soluble  in  water. 

Triatomic  alcohols  with  one  or  two  carbon  atoms  are  un- 
known, in  accordance  with  what  has  already  been  said  on  pp. 
131  and  188;  one  carbon  atom  binds  therefore  only  one 
hydroxyl. 

Thus  the  compound  CH{0H)3  is  incapable  of  existence,  but  we  know 
its  derivatives  ortho-formic  ether  (p.  149),  and  Formyl-tri  sulphonic 


GLYCERINK. 


199 


acid,  CH(S03H)3,  a  compound  resulting  from  the  action  of  fuming 
sulpluiric  acid  upon  calcium  metliyl-sulphonate  and,  like  other 
sulphonic  acids,  not  saponifiable. 

Ortho-acetic  ether,  CH3— C(OC2H5)3  (liquid,  B.  Pt.  142°),  and  its 
isomer,  Ethenyl  tri-ethyl  ether,  are  also  derivatives  of  non-existing  tri- 
hydroxylic  compounds. 


Glycerine,  jpropenyl  alcohol,  Oelsuss,^^  0^11^(011^).  (Scheeh, 
1779;  formula  established  by  Felouze  in  1836,  and  constitution 
by  Berthelot  and  Wurtz,) 

Synthesis.  By  heating  glyceryl  tri-chloride,  C3H5CI3  (p.  69), 
with  water  to  170° ; 

CH2CI-CHCI-CH2CI  +  3H2O      CH2(OH)-CH(OH)-CH2(OH)  +  3HC1. 

Glyceryl  trichloride  is  itself  obtainable  from  iso-propyl  iodide 
(which  can  also  be  prepared  synthetically),  by  conversion  into  propylene, 
addition  of  CI2,  and  heating  the  propylene  dichloride  formed  with 
chloride  of  iodine,  (Friedel  and  Silva)  : 

CsHeCl^  +  Cls  =  C3H5CI3  +  HCI. 

Glycerine  is  also  produced  by  the  oxidation  of  allyl  alcohol  with 
KMn04. 

The  constitution  of  glycerine  follows  from  this  synthesis  and 
also  from  its  relation  to  tartronic  acid  (p.  238) ;  each  of  the 
three  hydroxyls  is  attached  to  a  separate  carbon  atom. 

Preparation.  Glycerine  is  prepared  by  saponifying  the 
natural  fats  and  oils,  especially  olive  oil,  either  by  means  of 
superheated  steam,  or  by  heating  with  lime  and  water,  or  with 
sulphuric  acid.  These  are  thus  broken  up  into  their  com- 
ponents, the  glycerine  distilling  over  with  the  superheated 
steam,  and  being  at  the  same  time  purified  by  means  of  animal 
charcoal. 

In  the  manufacture  of  stearic  acid  (p.  162),  the  fats  are  saponified 
by  sulphuric  acid,  whereby  the  glycerine  is  converted  into  glyceryl- 
sulphuric  acid,  03X15(011)2(0.  SO3H),  from  which  it  can  be  obtained  by 
boiling  with  water  or  with  lime.  In  the  preparation  of  plaister,  by 
boiling  fats  with  lead  oxide  and  water,  as  at  p.  163,  an  aqueous  solution 
of  glycerine  is  got  along  with  the  insoluble  lead  plaister. 

Properties.  Thick  colourless  syrup.  Sp.  Gr.  1  -27.  Solidifies, 
when  strongly  cooled,  to  crystals  like  those  of  sugar  candy, 


200 


VIII.  POLYATOMIC  ALCOHOLS. 


which  melt  at  22°.  Boils  at  290°,  but,  when  impure,  it  can  be 
distilled  without  decomposition  only  under  diminished  pres- 
sure. Very  hygroscopic  and  miscible  with  water  and  alcohol 
in  all  proportions,  but  insoluble  in  ether. 

Uses.  In  the  manufacture  of  liqueurs,  fruit  preserves,  wine,  etc.  ; 
for  non-drying  stamp  colours  and  blacking  ;  when  mixed  with  glue,  in 
book  printing  ;  as  a  healing  ointment  for  external  use ;  but  especially 
in  the  manufacture  of  nitro-glycerine. 

Behaviour,  1.  It  forms  with  alkalies  and  other  metallic 
hydroxides  soluble  alcoholates  which  readily  break  up  again 
into  their  components. 

2.  By  exchanging  the  typical  hydrogen  atom  for  alkyl,  it  yields 
ethers,  e.g.  Mono-ethylin,  C3H5(OH)2(OC2H5),  and  Tri-ethylin, 
€3115(002115)3,  liquids  which  boil  without  decomposition. 

3.  As  an  alcohol  it  forms  the  most  various  ethers,  thus,  with 
sulphuric  acid,  the  easily  saponifiable  glyceryl-sulphuric  acid, 
C3H5(OH)2(O.S03H);  with  phosphoric  acid,  glyceryl-phosphoric 
acid,  03115(011)2(0. PO3H2) ;  with  nitric  acid,  nitro-glycerine, 
C3H5(O.N02)3 ;  with  hydrochloric  acid  the  chlorhydrins,  and 
with  the  higher  fatty  acids  the  fats.  For  its  behaviour  with 
hydriodic  acid,  or  iodine  and  phosphorus,  see  p.  65. 

4.  It  yields  compounds  of  a  mercaptan  or  aminic  character 
by  exchange  of  OH  for  SH  or  NH2. 

5.  By  the  separation  of  2  mols.  HgO,  it  yields  acrolein  (see 
p.  137),  and  by  the  indirect  separation  of  1  mol.  H2O,  glycidic 
alcohol  or  glycide,  C3Hg02. 

6.  Oxidizing  agents  convert  it,  according  to  circumstances, 
either  into  glyceric,  tartronic,  oxalic,  tartaric,  hydrocyanic, 
acetic,  or  formic  acid.  Halogens  oxidize  and  do  not  substi- 
tute. 

7.  It  yields  normal  butyl  alcohol,  caproic  acid  and  butyric 
acid  by  certain  fission-fungus  fermentations. 

Derivatives. 

Chlorhydrins,  (hydrochloric  ethers).  By  the  action  of  HCl, 
Mono-  and  Di-chlorhydrins  result,  and  by  the  action  of  PCI5 
upon  these,  Tri-chlorhydrin. 


DERIVATIVES  01'  GLYCERINE. 


201 


a  loiic-c  lorliydrin,  CH,(OH)— CH(OH)— Cir.Cl,  is  formed  from 
epiclilorhydrin,  Cj^Hr.O.Cl,  and  water;  a-Di-chlorhydrin,  CH.^C1— CH 
(OH)— CH.^Cl,  from  epiclilorhydrin  and  HCl ;  /3-Mono-chlorhydrin, 
CHglOH)— CHCl— CHslOH),  and  ]3-Di-clilorhydrin,  CH^IOH)— CHCl— 
CH2CI,  by  the  addition  of  ClOH  to  allyl  alcohol  or  allyl  chloride. 

The  chlorhydrins  are  liquids  more  or  less  easily  soluble  in 
water,  and  easily  soluble  in  alcohol  and  ether,  which  boil  at  a 
lower  temperature  than  glycerine.  They  may  also  be  regarded 
as  chlorinated  propylene  glycols  or  propyl  alcohols,  (tri-chlor- 
hydrin,  C3H5CI3,  as  trichloro-propane),  being  transformed  by 
backward  substitution  into  the  corresponding  alcohols  or 
propane. 

lodhydrins.  Mono-  and  Di-iodhydrin  are  known,  but  not 
Tri-iodhydrin,  (see  pp.  65  and  63). 

Glycide  compounds.  By  the  elimination  of  water  from 
glycerine  a  compound  is  obtained  which  unites  within  itself 
the  properties  of  ethylene  oxide  and  of  a  mon  atomic  alcohol, 
viz. : 

Glycide  alcohol,  C3H5O.  OH,  =  CH^^- — ^CH— CHyOH. 

It  may  be  prepared  e.g.  by  the  abstraction  of  HCl  from  a-mono- 
chlorhydrin,  by  means  of  baryta,  just  as  ethylene  chlorhydrin  yields 
ethylene  oxide.  It  is  a  colourless  liquid  boiling  at  162°,  and  miscible 
with  water,  alcohol  and  ether,  which  recombines  with  HgO  to  glycerine 
and  with  HCl  to  chlorhydrin,  and,  as  an  alcohol,  forms  ethers  (glycide 
ethers),  etc.  It  reduces  an  ammoniacal  silver  solution.  Is  isomeric 
with  propionic  acid.    Its  hydrochloric  ether  is 

Epichlorhydrin,  C3H5O.CI,  isomeric  with  chlor-acetone  and  pro- 
pionyl  chloride,  a  mobile  liquid  of  chloroform  odour,  boiling  at 
117°,  which  is  formed  by  the  separation  of  HCl  from  either  of  the 
di-chlorhydrins,  and  is  capable  of  recombining  with  HgO,  HCl,  etc. 

Ethers  of  Nitric  acid.  Mono-nitrin,  C3H5(OH)2(O.N02), 
and  Tri-nitrin  or  Nitro-gly carina,  6311^(0. NOg)^,  are  known. 
The  latter  is  prepared  by  treating  glycerine  with  a  cold 
mixture  of  concentrated  nitric  and  sulphuric  acids.  It  is  a 
colourless  oil,  insoluble  in  water,  poisonous,  and  of  a  sweet 
burning  aromatic  taste.  Sp.  Gr.  1'6.  Solidifies  at —20°.  It 
burns  without  explosion,  but  explodes  with  terrible  violence 
when  quickly  heated  or  when  struck,  {NoheVs  explosive  oil). 


202 


VIII.   POLYATOMIC  ALCOHOLS. 


When  mixed  with  kieselguhr  in  the  proportion  of  3  parts  to  1, 
it  forms  dynamite,  (Nobel,  1867),  which  is  not  affected  by 
percussion^  (B.  9,  1802),  but  is  exj^loded  by  fulminate  of 
mercury  with  frightful  force.  It  is  saponified  by  alkalies  and 
by  sulphide  of  ammonium. 

Ethers  of  Organic  acids.  Mono  formin,  C3H5(OH)2(O.CHO), 
already  mentioned  at  p.  154,  is  an  oily,  easily  saponifiable 
liquid,  which  yields  allyl  alcohol  upon  heating. 

The  Acetins  are  high-boiling  liquids  soluble  in  water  and 
ether,  which  can  be  prepared  synthetically,  and  which  are 
used  technically  for  the  solution  of  colours  for  printing. 

Mono-,  Di-,  and  Tri-palmitin,  C3H5(OH)2(O.0igH3;^O),  etc., 
can  likewise  be  obtained  by  synthesis,  and  melt  respectively 
at  58°,  59°,  and  66°.  Tri-palmitin,  G^}i^{0,G-^QH^fi)^,  may  be 
prepared  from  palm  oil  (p.  163),  and  forms  glancing  mother- 
of-pearl  plates;  Tri-stearin,  G^'H.^(O.G-^^^B.^fi)^,  from  mutton 
tallow  or  shea  butter,  M.  Pt.  72° ;  Tri-olein,  03115(0.01811330)3, 
the  chief  constituent  of  olive  oil,  is  an  oil  which  only  solidifies 
at  —6°,  For  the  animal  and  vegetable  fats  and  oils,  see  p. 
162. 

0.  Tetra-,  Penta-,  and  Hexatomic  Alcohols. 

These  alcohols  can  react  respectively  with  four,  five,  or  six 
molecules  of  a  monobasic  acid  to  form  neutral  ethers,  and  con- 
sequently four,  five,  or  six  alcoholic  hydroxyls  are  to  be 
assumed  as  present  in  their  molecules. 

The  atomicity  of  an  alcohol  is  determined  by  the  number  of  acetyl 
groups  which  are  found  to  be  present  in  the  ether  which  results  upon 
heating  it  with  acetic  anhydride  and  acetate  of  soda,  thus  : 

The  ether  of  any  alcohol  in  question  may  also  be  prepared  by  the  aid 
of  an  acid  containing  halogen,  bromo-benzoic  acid  being  especially  suit- 
able for  this ;  and  from  the  amount  of  bromine  found  in  the  ether,  the 
number  of  acid  radicles  which  have  entered  the  molecule,  i.e.  the 
number  of  replaced  hydroxyls,  can  be  deduced. 

The  higher  atomic  alcohols  are  solid  crystalline  compounds 


TETRA-  TO  HEXATOMIC  ALCOHOLS. 


203 


of  sweet  taste.  As  a  rule  tliey  cannot  be  volatilized  without 
decomposition.  Their  derivatives  are  exactly  analogous  to 
those  of  glycol  and  glycerine. 

Their  constitution  follows  from  the  law  already  repeatedly 
referred  to  at  pp.  131,  188,  etc.,  viz.,  that  not  more  than  one 
hydroxyl  group  can  be  bound  to  one  carbon  atom  without  the 
immediate  separation  of  water,  so  that  a  tetratomic  alcohol 
must  contain  at  least  four,  and  a  hexatomic  alcohol  at  least 
six  atoms  of  carbon.  The  tetratomic  alcohol  erythrite, 
=  C4Hg(OH)4,  has  thus  the  formula : 

CH2(0H)— CH(OH)— CH(OH)— CH2(0H) ; 

and  mannite,  the  lowest  of  the  hexatomic  alcohols,  CgH^^Og, 
=  CgHg(OH)g,  the  formula  : 

CH2(0H)~CH(0H)— CH(OH)— CH(OH)— CH(OH)— CH2(0H). 

These  alcohols,  which  are  the  lowest  theoretically  possible, 
which  contain  the  smallest  possible  number  of  carbon 
atoms  in  the  molecule,  are  at  the  same  time  the  only  ones  of 
special  importance. 

1.  Tetratomic  alcohols.  Ortho-carbonic  ether,  Basset'' s  carbonic  ether, 
€(002115)4,  is  to  be  regarded  as  the  ether  of  the  hypothetical  alcohol, 
0(0H)4,  which  may  be  looked  upon  as  the  hydrate  of  carbonic  acid,  but 
is  itself  incapable  of  existence.  It  is  a  liquid  of  ethereal  odour,  boiling 
at  159°. 

Erythrite,  erythroglucine  or  phycite,  C4Hg(OH)4,  {Stenhouse),  occurs  in 
the  free  state  in  Protococcus  vulgaris,  and  combined  with  orsellinic  acid 
as  ether  (erythrin),  in  many  lichens  and  algse.  Large  quadratic 
crystals,  difficultly  soluble  in  alcohol  and  insoluble  in  ether.  M.  Pt. 
112°,  B,  Pt.  about  300°.  Yields  secondary  butyl  iodide  when  heated 
with  hydriodic  acid,  (pp.  84  and  63,  3  b). 

Nitro-erythrite,  C4Hg(O.N02)4,  forms  glancing  plates,  and  resembles 
nitro-glycerine  in  explosibility. 

2.  Pentatomic  alcohols  of  the  methane  series  are  unknown.  (Of. 
Quercite). 

3.  Hexatomic  Alcohols.  Mannite,  CgHj^O^j,  =  CgHg(OH)g, 
{Proust,  1800),  is  found  in  many  plants,  for  instance,  in  the 
larch,  in  Viburnum  Opulus,  in  celery,  in  the  leaves  of  Syringa 
vulgaris,  in  sugar  cane,  in  Agaricus  integer  (of  the  dry  sub- 
stance of  which  it  forms  20%),  in  rye  bread,  and  especially  in 


204 


VIII.  POLYATOMIC  ALCOHOLS. 


the  manna  ash,  Fraxinus  ornus,  the  dried  juice  of  which  con- 
stitutes manna.  It  can  be  prepared  from  grape  sugar,  or,  still 
better,  from  fruit  sugar,  from  which  it  only  differs  in  composi- 
tion by  containing  two  atoms  of  hydrogen  more,  by  reduction 
with  sodium  amalgam : 

Fine  needles  or  rhombic  prisms,  easily  soluble  in  cold  water 
and  boiling  alcohol.  M.  Pt.  166°.  When  heated  it  is  con- 
verted into  its  anhydrides,  Mannitan,  CgH^gOg,  and  Mannide, 
CgHjoO^.  Cautious  oxidation  converts  mannite  first  into 
laevulose,  (B.  19,  911),  mannose  (p.  289)  being  formed  at  the 
same  time.  Nitric  acid  oxidizes  it  to  saccharic  acid,  while 
hydriodic  reduces  it  to  hexyl  iodide,  (p.  66). 

Nitro -mannite,  CgTl8(O.N0.2)6,  forms  glancing  needles  and  is  explosive. 
The  Acetate,  CgH8(O.C2H30)6,  is  prepared  from  acetic  anhydride. 

Dulcite,  melampyrine,  CeHglOHjg,  is  isomeric  with  mannite  and,  like 
the  latter,  is  widely  distributed  in  nature,  being  found  e.g.  in  the 
varieties  of  melampyrum  and  evonymus,  in  the  dulcite  manna  of 
Madagascar,  etc.  Large  monoclinic  prisms.  Nitric  acid  oxidizes  it  to 
mucic  acid,  and  hydriodic  acid  reduces  it  to  the  same  hexyl  iodide  as  in 
the  case  of  mannite.  The  reason  of  the  isomerism  of  these  two  com- 
pounds is  not  yet  known. 

Sorbite,  CoRifiQ  +  iHgO,  is  related  to  the  above. 

The  carbohydrates  are  closely  related  to  the  hexatomic 
alcohols.  The  latter  differ  from  the  former  in  not  being 
fermentable  by  yeast,  in  not  reducing  an  alkaline  cupric 
solution,  dulcite  alone  excepted,  and,  excepting  iso-dulcite, 
in  being  optically  inactive. 


Oxidation  Products  of  the  Polyatomic  Alcohols. 

By  the  oxidation  of  the  polyatomic  alcohols  there  result,  or 
may  result,  not  only  aldehydes,  ketones  and  acids,  but  also 
numerous  compounds  which  possess  a  double  chemical  nature 
in  so  far  as  they  unite  in  themselves  the  characteristics  of 
several  of  these  classes  of  compounds.    These  are  the  aldehyde- 


OXIDATION  PRODUCTS  OF  THE  TOLYATOMIC  ALCOHOLS.  205 


alcohols,  which  are  at  the  same  time  aldehyde  and  alcohol,  the 
ket one-alcohols,  at  the  same  time  ketone  and  alcohol,  the 
alcohol-acids,  aldehyde-acids,  ketone-acids  and  ketone-alde- 
hydes. 

An  aldehyde- acid,  for  instance,  is  capable,  as  an  acid,  of 
forming  salts,  ethers  and  amides  on  the  one  hand,  compounds 
which  possess  all  the  characteristic  properties  of  the  ethers, 
etc. ;  and  on  the  other,  as  an  aldehyde,  it  is  able  to  reduce  an 
ammoniacal  silver  solution,  to  combine  with  NaHSOg,  and  to 
react  with  hydroxylamine,  etc. 

Summary  of  the  Oxidation  Products. 

(a)  Of  the  diatomic  di-primary  alcohols, 
CHO. 
CHO 
Glyoxal. 


CH2.OH 
CH2.OH 
Glycol. 


CH2.OH 
CHO 


CH2.OH 
->CO.OH 


CHO  ^ 
■CO.  OH 


CO.  OH 
CO.  OH 
Oxalic  acid. 


GlycoUic  aldehyde.  Glycollic  acid.  Glyoxalic  acid. 

Possible  products :  diatomic  aldehydes,  dibasic  acids,  alcohol- 
aldehydes,  alcohol-acids,  aldehyde-acids. 


(b)  Of  the  diatomic  primary-secondary  alcohols. 

CH3  CH3 

rCO   >-G0 

CH2.OH  CHO 
Acetone-alcohol.  (Unknown). 


CH3 
CH.OH 
CH2.OH 

a- Propylene 
glycol, 


CH3  / 
CH.OH 
CO.  OH 


CH3 

^CO 

CO.OH 

Pyro-racemic 
acid. 


02  OJ 

f  .2^ 


^,0 

O  rO 


(Lactic  aldehyde,  Lactic  acid. 

unknown).  ' 

Possible  products  :  aldehyde-alcohols,  ketone-alcohols,  ketonc- 
aldehydes,  alcohol-acids,  ketone-acids. 

(c)  Of  the  diatomic  di-secondary  alcohols:  di-ketones.  (No  dibasic 
acids  or  alcohol-acids,  Cn). 


206 


IX.  POLYATOMIC  MONOBASIC  ACIDS. 


{d)  Of  the  other  diatomic  alcohols  :  easy  to  tabulate. 

(e)  The  tri-  and  polybasic  alcohols  are  capable  of  yielding  the  most 
various  products  upon  oxidation,  especially  polyatomic  ketone-alcohols, 
alcohol  acids,  ketone-acids,  and  polybasic  acids. 


The  most  important  among  these  compounds  are  the  alcohol- 
acids,  (di-,  tri-,  etc.  atomic  monobasic,  tri-  etc.  atomic  dibasic 
acids,  and  so  on),  and  the  polybasic  acids ;  the  ketonic  acids 
also  call  for  especial  interest. 


IX.  POLYATOMIC  MONOBASIC  ACIDS  AND 
COMPOUNDS  RELATED  TO  THEM. 

A.  Diatomic  Monobasic  Acids. 

Summary. 


Glycollic  acid, 

CH2(OH)(C02H) 
Oxy-propionic  acids, 

C2H4(OH)(C02H) 
Oxy-butyric  acids, 


Oxy-valeric  acids, 

C4H8(OH)(C02H) 
Oxy-caproic  acids, 

C5Hio(OH)(C02H) 

etc. 


The  diatomic  alcohol-acids  or  diatomic  monobasic  acids  are 
compounds'which  unite  in  themselves  the  characteristics  of  an 
alcohol  and  of  an  acid,  and  are  consequently  capable  of  forming 
derivatives  as  alcohols,  as  acids,  and  as  both  together. 

These  derivatives  are  in  part  easily  saponifiable,  and  corre- 
spond therefore  with  the  acid  derivatives,  i.e.  the  compound 
ethers,  chlorides  and  amides;  in  part  they  are  relatively  stable 
as  regards  saponifying  agents,  and  therefore  correspond  with 
the  alcoholic  derivatives,  i.e.  the  ethers,  amine  bases,  etc.,  (see 
table,  p.  211). 


DIATOMIC  MONOBASIC  ACIDS. 


207 


The  lowest  members  of  the  scries  of  diatomic  monobasic 
acids,  which  are  at  the  same  time  the  most  important,  are 
glycollic  acid  and  lactic  acid,  both  syrupy  liquids  which  solidify 
to  crystalline  masses  in  the  exsiccator,  and  easily  give  up 
water  to  form  anhydride. 

They  cannot  be  volatilized  without  decomposition.  They 
are  readily  soluble  in  water,  and  for  the  most  part  also  in 
alcohol  and  ether. 

They  are  termed  diatomic,  because  they  may  result  from 
the  oxidation  of  the  diatomic  alcohols,  and  contain  in  accord- 
ance with  theory  two  hydroxyls.  As  acids  they  are  mono- 
basic. They  are  also  frequently  called  oxy-fatty  acids,  on 
account  of  their  being  derived  from  the  fatty  acids  by  the 
exchange  of  one  hydrogen  atom  for  hydroxy  1,  in  the  same  way 
as  the  alcohols  are  derived  from  the  hydrocarbons  : 

CH3 — COgH,  acetic  acid ;  CH2(0H) — COgH,  oxy-acetic  acid. 

We  may  also  regard  them  as  carboxylic  acids  of  the  mona- 
tomic  alcohols,  e.g,  lactic  acid,  C2H4(OH).C02H,  is  ethyl 
alcohol-carboxylic  acid. 

Formation,  1.  By  the  regulated  oxidation  of  the  glycols, 
(see  Summary,  p.  205). 

2.  From  the  fatty  acids,  through  their  mono-haloid  substitu- 
tion products,  the  halogen  of  these  being  easily  replaced  by 
hydroxyl,  either  by  means  of  moist  oxide  of  silver  or  often  by 
prolonged  boiling  with  water  alone.  Glycollic  acid  is  thus 
obtained  from  mono-chloracetic  acid  ; 

CH2CI.CO2H  +  H2O  =  CH2(0H).C02H  +  HC1. 

For  a  reaction  of  these  haloid-substitution  products  in  a 
different  direction,  see  /?-  and  y-oxyacids, 

3.  From  the  aldehydes  and  ketones  containing  one  atom  of 
carbon  less,  by  the  preparation  of  their  hydrocyanic  acid  com- 
pounds, (see  pp.  133  and  142),  and  saponification  of  the  latter. 
Thus,  from  aldehyde  is  produced  ethylidene  cyanhydrin,  and 
from  this  lactic  acid  : 


CH3.CH(OH)(CN)4-2H20 


=  CH3.CH(OH).C02H  +  NH, 


208 


IX.  POLYATOMIC  MONOBASIC  ACIDS. 


Since  the  aldehydes  and  ketones  are  easily  got  from  the  correspond- 
ing alcohols,  this  reaction  furnishes  a  means  of  preparing  the  acids, 
CuH2n(0H)  (CO2H),  from  the  alcohols,  CnH2n+i(0H),  of  introducing 
carboxyl  into  the  latter  in  place  of  hydrogen  ;  this  is  a  very  important 
synthesis. 

4.  From  the  glycollic  cyanhydrins  by  saponification,  e.g. 
ethylene  lactic  acid  from  ethylene  cyanhydrin : 

CH,(OH)— CH2.CN  +  2H2O  =  CH2(0H)— CH2— CO2H  +  NH3 

The  cyanhydrins  being  easily  obtained  from  the  glycols,  this  for- 
mation of  oxy-acids  represents  an  exchange  of  a  hydroxyl  of  the  glycol 
for  carboxyl,  and  is  analogous  to  the  formation  of  acetic  acid  from 
methyl  alcohol. 

5.  By  the  reduction  of  aldehyde-acids  or  ketonic  acids,  e.g.  lactic 
from  pyroracemic  acid  (p.  223).  This  reaction  corresponds  with  the 
formation  of  the  alcohols  from  the  aldehydes  or  ketones  by  reduction. 

6.  By  the  action  of  nitrous  acid  (N2O3)  upon  amido-acids  (see 
glycocoll) ;  a  reaction  analogous  to  the  formation  of  alcohols  from 
amines. 

Constitution  and  Isomers.  As  oxy-compounds  of  the  fatty 
acids,  the  acids  of  the  foregoing  series  can  exist  in  as  many 
modifications  as  there  are  possible  mono-haloid  substitution 
products  of  the  fatty  acids.  Thus  there  is  only  one  glycollic 
acid,  corresponding  to  mono-chloracetic  acid,  but  two  lactic 
acids — corresponding  to  a-  and  /3-chloro-propionic  acids — are 
possible,  and  both  actually  exist ;  they  are  designated  as  a- 
and  ^-oxy-propionic  acids : 

CH3— CHCl— CO2H  CH3— CH(OH)— CO2H 

a-Chloro-propionic  acid.        a-Oxy-propionic  acid  or 

common  lactic  acid. 

CH2I— CH2— CO2H  CH2(0H)— CH2-  CO2H 

/8-Iodo-propionic  acid.  /3-Oxy-propionic  acid  or 

ethylene  lactic  acid. 

From  the  two  butyric  acids  can  be  theoretically  derived : 
(a)  From  the  normal  acid  : 

CH3 — CH2 — CH2 — CO2IIJ 
7       P  a 
an  a-,  jS-,  and  7-oxy-butyric  acid ; 


DIATOMIC  MONOBASIC  ACIDS. 


209 


(6)  From  iso-butyric  acid  : 

an  a-  and  j8-oxy-isobutyric  acid. 

The  constitution  of  these  oxy-acids  is  often  apparent  from 
their  formation  alone.  Thus  the  preparation  of  common  lactic 
acid  from  aldehyde,  CH3 — CHO,  according  to  method  3,  shows 
that  it  contains  the  group  CH3 — CH=,  "  ethylidene" ;  it  is 
therefore  termed  "ethylidene  lactic  acid."  On  the  other  hand 
the  formation  of  /?-oxy-propionic  acid  from  glycol,  i.e.  glycol 
cyanhydrin,  according  to  4,  is  a  proof  of  its  containing  the 
group  — OH2 — CH2 — ,  "ethylene";  hence  the  name  "ethylene 
lactic  acid." 

The  behaviour  of  the  oxy-acids  usually  explains  their  constitution 
also  ;  if  they  can  be  oxidized,  for  instance,  to  dibasic  acids  (which  con- 
tain two  carboxyis),  then  they  must  contain  a  primary  alcohol  group, 
— CH2.OH,  since  only  such  a  group  yields  a  new  carboxyl  on  oxidation. 
Ethylene  lactic  acid  is  therefore  a  primary"  alcohol-acid.  Its  isomer, 
ethylidene  lactic  acid,  is  similarly  a  "secondary"  alcohol-acid,  while 
a-oxy-isobutyric  acid  is  a  "tertiary"  alcohol-acid,  i.e.  acid  and  tertiary 
alcohol  at  the  same  time. 

Behaviour.  1.  The  double  chemical  character  of  the  oxy- 
acids  will  be  gone  into  more  particularly  under  glycoUic  acid. 
As  acids  they  form  salts,  compound  ethers  and  amides;  as 
alcohols  they  yield  ethers,  amines,  etc.  Among  those  deriva- 
tives the  alcoholic  amines  of  the  acids,  the  so-called  amido- 
acids,  are  of  especial  interest.    (See  Glycocoll,  p.  212). 

2.  The  oxy-acids  form  different  kinds  of  anhydrides,  viz.: — 
(a)  as  alcohols,  (see  di-glycollic  acid) ;  (6)  one  molecule  as 
alcohol  forms  with  a  second  molecule  as  acid,  a  compound 
ether,  with  separation  of  HgO,  (see  glycollic  anhydride) ;  (c) 
such  a  formation  of  ether  as  this  proceeds  a  second  time,  (see 
glycolide) ;  (d)  one  molecule  loses  H2O,  with  formation  of  an 
"  intra-molecular  "  anhydride,  a  so-called  lactone,  (see  p.  218). 

3.  For  behaviour  upon  oxidation,  see  p.  205,  and  also  the 
individual  compounds. 

4.  Just  as  the  alcohols  go  into  olefines  with  separation  of  water,  so 

(50(5)  O 


210 


IX.  POLYATOMIC  MONOBASIC  ACIDS. 


can  many  of  the  oxy -acids,  especially  the  be  transformed  into 
unsaturated  monobasic  acids.    (See  hydracrylic  acid,  p.  216), 

5.  Halogens  oxidize  and  do  not  substitute. 

6.  Warming  with  HI  gives  rise  to  the  corresponding  fatty^ 
acids,  just  as  the  alcohols  are  converted  by  this  reagent  into 
hydrocarbons. 

7.  When  the  a-oxy-acids  are  warmed  with  dilute  sulphuric  acid, 
formic  acid  is  separated  and  the  aldehyde  or  ketone  which  would  give 
rise  to  the  acid,  according  to  method  3,  is  reproduced.  The  jS-oxy-acids 
on  the  other  hand  break  up  in  this  way,  and  also  when  heated  alone, 
into  water  and  acids  of  the  acrylic  series.  The  a-,  7-,  etc.  oxy-acids 
also  differ  from  each  other  in  the  facility  with  which  they  form 
anhydrides.    (See  Lactones. ) 


GlycoUic  acid,  CH2(0H)— CO.OH,  (Strecker,  1848). 
Occurrence.    In  unripe  grapes  and  in  the  leaves  of  the  wild 
vine,  etc. 

Formation,  (See  also  p.  207.)  1.  By  the  oxidation  of  glycol 
with  dilute  HNO3,  (Wurtz), 

2.  Together  with  glyoxal  and  glyoxalic  acid,  by  the  oxida- 
tion of  alcohol  with  dilute  HNO3.  Further,  by  the  oxidation 
of  glucoses  by  Ag20,  (A.  205,  193). 

3.  By  the  reduction  of  oxalic  acid  with  Zn  +  H2SO4. 

4.  Preparation  from  mono-chloracetic  acid,  according  to 
p.  207  ;  best  when  boiled  with  marble.    (A.  200,  76). 

Properties,  Colourless  needles  or  plates,  stable  in  the  air, 
and  easily  soluble  in  water,  alcohol  and  ether.  M.  Pt.,  80°. 
Nitric  acid  oxidizes  it  to  oxalic  acid.  The  alkaline  salts  are 
hygroscopic,  the  calcium  salt  and  the  magnificent  blue  copper 
salt  sparingly  soluble  in  water. 

Derivatives.  (See  table,  p.  211.)  As  an  acid,  gly collie  acid 
forms  salts,  compound  ethers, — e.g.  glycollic  ethyl  ether, — a 
chloride,  glycollyl  chloride,  and  glycollamide,  all  of  which  are 
readily  saponified,  some  of  them  even  on  warming  with  water. 
All  those  derivatives  still  retain  their  alcoholic  character.  If, 
on  the  other  hand,  glycollic  acid  forms  derivatives  as  an  alcohol, 
the  properties  of  the  alcoholic  derivatives  in  question  are' 
combined  with  those  of  an  acid,  since  the  hydroxyl  of  the 


GLYCOLLIC  ACID. 


211 


alcoholic  group,  — CH2.OH,  enters  into  reaction,  while  the  car- 
boxyl  group  remains  unchanged.  These  derivatives  are  either 
ethers,  such  as  ethyl-glycollic  acid  (see  table),  or  e.g,  amines, 
such  as  glycocoll,  and,  as  alcoholic  derivatives,  they  are  not 
saponifiable ;  or  they  are  compound  ethers  of  glycollic  acid  as 
alcohol,  e.g.  acetyl-gly  collie  acid,  CH2(O.C2H30) — CO2H, 
or  mono-chloracetic  acid,  CHg.Cl — COgH  (the  hydro- 
chloric ether  of  glycollic  acid),  and  then  they  are  of  course 
saponifiable.  These  latter  compounds  still  retain  their  acid 
character  and  therefore  form,  on  their  part,  compound  ethers, 
chlorides  and  amides,  which  are  readily  broken  up  backwards 
by  saponification.  The  following  table  gives  a  summary  of 
the  more  important  derivatives  of  glycollic  acid. 


Acid  Derivatives. 

Alcoholic  Derivatives. 

Mixed  Derivatives. 

CH2(0H)— CCONa 
Sodium  glycollate. 

CH2(0Na)— CO.ONa 
Di-sodium  glycollate. 

Hygroscopic  ;  decomp. 

by  HgO  into  Na  salt  and 
NaOH. 

CH2(0H)— CO.OC2H5 
Ethyl  glycollate. 
Liquid,  B.  Pt.  160°. 

CHslOCaHg)— CO.OH 
Ethyl-glycollic  acid. 
Liquid,  B.  Pt.  206°. 

CH2(0C2H;)-C0(0C2H5) 
Ethylic  ethyl-glycollate. 
Liquid,  B.  Pt.  158°. 

CH2(0H)— CO.Cl 
Glycollyl  chloride. 
Oil ;  decomposes  on 
volatilizing. 

CH2CI— CO.OH 
Mono-chloracetic 
acid. 

CH2CI— COCl 
Mono-chlor-acetyl 
chloride.    Liquid,  B.  Pt. 
120°,  of  suffocating  odour. 

CH2(0H)— CO.NH2 
GlycoUamide. 
Crys.  M.Pt.  120°;  does 
not  form  salts  with 
bases. 

CH2(NH2)— CO.OH 

Glycocoll. 
Crys.    M.  Pt.  170°. 
Forms  salts  with  acids 
and  bases. 

CH2(NH2)-CO(NH2) 
Glycocollamide. 
Crys. 

To  the  compounds  of  the  second  vertical  row  belong  also,  among 
others,  Thio-glycoUic  acid,  CH2(SH)— CO.OH,  which  is  at  the  same 
time  an  acid  and  a  mercaptan ;  to  those  of  the  third  row  belong  mixed 
compounds  such  as  CH2(NH2)— CO(OC2H5),  (see  glycocoll).  It  is  easy 
to  see  that  the  corresponding  derivatives  of  the  first  and  second  vertical 
rows  are  always  isomeric. 


212 


IX.  POLYATOMIC  MONOBASIC  ACIDS. 


Anhydrides  of  GlycoUic  acid.  1.  Di-gly collie  acid,  C4HgOg,  = 
0(CH2 — C0.0H)2,  is  an  alcoholic  anhydride  and  a  dibasic  acid.  It  is 
obtained  e.g.  by  boiling  mono-chloracetic  acid  with  lime.  Large 
rhombic  prisms.  Being  an  alcoholic  ether,  it  is  not  saponified  on  boil- 
ing with  alkalies,  but  on  heating  with  concentrated  hydrochloric  acid 
to  120°. 

2.  GlycoUic  anhydride,  C4H6O5,  =  CHaCOH)— C0.0(CH2— CO.OH), 
is  a  compound  ether-anhydride,  which  is  formed  upon  heating  glycollic 
acid  to  100°.    It  becomes  hydrated  again  when  boiled  with  water. 

CH2— 0— CO 

3.  Glycolide,  C4H4O4,  =   |  |      is  an  ether-acid  anhydride 

CO  0— CH2, 

isomeric  with  fumaric  acid,  which  results  when  glycollic  acid  is  heated 
strongly.  It  is  a  powder,  almost  insoluble  in  water,  and  also  becomes 
hydrated  again  upon  boiling  with  water. 

Glycocoll,  glycocine,  amido-acetic  acid,  CH2(NH2) — CO.  OH, 
(Braconnot,  1820).  This  is  the  simplest  representative  of  the 
important  class  of  "  amido-acids,"  so  called  because  they  are 
derived  from  the  fatty  acids  by  the  exchange  of  a  hydrogen 
atom  of  the  hydrocarbon  radicle  for  amidogen,  e.g.  CH3.CO2H, 
acetic  acid;  GH2(NH2).C02H,  amido-acetic  acid.  Its  methods 
of  formation  include  those  of  the  other  amido-acids. 

Formation.  1.  By  heating  mono-chloracetic  acid  with 
ammonia  : 

CH3CI— CO2H  +  2NH3  =  CH2(NH2)— CO2H  +  NH/Jl, 
{Heintz,    A.   122,    261).      Di-   and   Tri-glycollamic  acids, 
NH(CH2— C02H)2  and  N(CH2— C02H)3,  are  produced  at  the 
same  time. 

a-Chloropropionic  acid  in  like  manner  yields  alanine  with 
ammonia,  (see  lactic  acid),  and  so  on. 

2.  By  boiling  glue  with  alkalies  or  acids. 

3.  Together  with  benzoic  acid  by  decomposing  hippuric 
acid,  i.e.  benzoyl-glycocoll,  by  HCl : 

CH2[1S[H(C0C6H5)]-C02H  +  H,0  =  CHalNHJCO^H  +  CeHgCO.OH. 

Hippuric  acid.  Benzoic  acid. 

4.  Together  with  cholic  acid,  by  the  analogous  decomposition  of 
glycocholic  acid,  C26H43NO6. 

5.  From  cyano-carbonic  ether,  CN — CO.OC2H5,  and  nascent  hydro- 
gen, or  from  cyanogen  and  liydriodic  acid  : 

CN— CN  +  2H2  +  2H2O  =  CHglNHg)— CO.OH  -f-  NH3. 


GLYGOCOLL. 


213 


6.  (Of  the  homologues  of  glycocoll)  :  By  treating  ethylidene-cyan- 
hydrin  (p.  133)  etc.  with  alcoholic  ammonia,  or  aldehyde-ammonias  with 
hydrocyanic  acid,  amido-cyanides  are  formed,  e.g.  CH3 — CH(NH2)(CN), 
which  are  saponified  to  amido-acids  upon  boiling  with  HCi. 

Properties,  Glycocoll  forms  large  colourless  rhombic  prisms, 
easily  soluble  in  water,  but  insoluble  in  absolute  alcohol  and 
ether.  It  has  a  sweet  taste,  hence  the  name  "gelatine  sugar" 
or  glycocoll  (yAi^Kus,  sweet,  KoXXa,  glue).  It  melts  at  170°, 
and  decomposes  on  being  heated  more  strongly. 

Behaviour.  Glycocoll,  like  all  the  amido-acids,  unites  in 
itself  the  properties  of  a  base  (being,  as  an  alcoholic  amine,  non- 
saponifiable)  and  those  of  an  acid.  It  therefore  forms  salts  with 
acids  as  well  as  with  bases,  e.g.  glycocoll  hydrochlorate, 
CgHgNOg.HCl,  which  crystallizes  in  prisms,  and  the  char- 
acteristic copper  salt,  glycocoll  copper,  {G<^^O^^G\\  +  HgO, 
which  crystallizes  in  blue  needles,  the  latter  being  obtained  by 
dissolving  copper  oxide  in  a  solution  of  glycocoll.  Most  of  the 
other  amido-acids  also  form  characteristic  copper  salts  of  this 
nature,  which  serve  for  their  separation.  Glycocoll  also  yields 
compounds  with  salts,  and,  as  an  acid,  forms  an  ethyl  ether, 
an  amide,  etc.,  (see  table,  p.  211).  Heated  with  BaO,  it  is 
decomposed  into  methylamine  and  COg,  while  N2O3  converts  it 
into  glycollic  acid,  (the  normal  reaction  of  the  primary  amines). 
Ferric  chloride  produces  with  it  an  intensive  red,  and  copper 
salts  a  deep  blue  colouration. 

Glycocoll  ethyl  ether  yields  with  NgOg  the  interesting  Diazo-acetic 
ether,  CNgH— CO.OC2H5.    (B.  16,  2230;  17,  953;  18,  1283). 

Constitution^  (see  B.  16,  2650).     Free  glycocoll  may  be 
regarded  as   an   intramolecular  salt,  corresponding  to  the 
NH 

formula,  GH2<^qq        (see  betaine). 
Alkyl  derivatives  of  Glycocoll ; 

Methyl-glycocoll       Tri-methyl-glycocoll  Acetyl-glycocoU 
or  Sarcosine,  or  Betaine,  or  Aceturic  acid, 


CH2— NH(CH3) 
CO.OH 


CH2-N(CH3). 

co.o 


CH2— NHlCaHgO) 
CO.OH. 


(a  decomposition 


(contained  in  beetroot 
and  related  to 
choline). 


etc. 


product  of  creatine 
and  caffeine). 


214 


IX.  POLYATOMIC  MONOBASIC  ACIDS. 


The  above  have  all  been  prepared  synthetically. 

Lactic  acids,  CgHgOg,  =  C2H4(OH)(C02H).  {Wislkenus, 
A.  128,  1 ;  166,  3 ;  167,  302,  346).  As  has  been  already 
mentioned  at  p.  208,  two  isomeric  lactic  acids  are  theoretic- 
ally possible,  viz.,  a-  and  /5-oxy-propionic  acids,  or  ethylidene- 
and  ethylene-lactic  acids.  Both  are  known,  the  former  being 
the  common  lactic  acid.  There  exists,  however^  in  addition 
to  these,  a  third  modification,  sarco-lactic  acid,  which  is 
chemically  identical  with  the  a-acid,  but  differs  from  it  in 
physical  properties. 

The  minute  investigation  of  the  different  lactic  acids  has  been  of  very 
great  importance  for  the  development  of  chemical  theory ;  they  were 
formerly  held  to  be  dibasic,  and  the  recognition  of  their  diatomic 
monobasic  nature  has  materially  contributed  to  the  acceptation  of  the 
theory  of  the  linking  of  atoms. 


Modes  of  Formation. 


1.  By  the  regulated  1 

oxidation  of  j 

2.  By  the  exchange 

of  halogen  for  |- 
hydroxyl  from  J 

3.  By  saponification) 

of  / 

4.  By  action  of  N203\ 

upon  / 

5.  By  the  reduction  \ 

of  I 


Fermentation  lactic  acid, 


a-Propylene  glycol, 
CH3-CH(OH)-CH2(OH). 

a -Chloro -propionic  acid, 
CH3—CHCI— CO.OH. 


Aldehyde-cyanhydrin, 
CH3— CH(OH)— CN. 

Alanine, 
CH3-CH(NH2)-CO.OH. 

Pyro-racemic  acid, 
CHo— CO— CO.OH. 


6.  By  the  lactic  fermentation  of  sugar,  etc. 


Ethylene-lactic  acid. 


/3-Propylene  glycol, 
CH2(OH)-CH2-CH2(OH) 

/3-Iodo-propionic  acid, 
CH2I—CH2— CO.OH. 


Ethylene-cyanhydrin, 
CH2(0H)— CHa— CN. 


1.  Ethylidene-lactic  acid,  CH3— CH.(OH)— COgH.  Dis- 
covered by  Scheele,  and  recognised  as  oxy-propionic  acid  by 
Kolbe,    Occurs  in  opium,  sauerkraut,  and  in  the  gastric  juice. 

Preparation.  This  depends  upon  the  so-called  lactic  fermen- 
tation of  sugars,  e,g,  milk,  cane  and  grape  sugars,  and  of 


LACTIC  ACID. 


215 


substances  related  to  them,  such  as  gum  and  starch ;  it  is 
effected  in  presence  of  decaying  albuminous  compounds,  for 
instance,  old  cheese,  by  the  action  of  oval  micro-organisms — 
(lactic  bacteria) — if  the  solution  is  nearly  neutral.  This  last 
condition  is  attained  by  the  addition  of  zinc  white  or  chalk  to 
the  fermenting  mixture.  The  fermentation  is  completed  in 
eight  to  ten  days  at  a  temperature  of  40°-4:5°;  should  it  be 
prolonged,  it  changes  into  the  butyric  fermentation  (p.  159). 
The  free  acid  is  then  liberated  from  the  lactate  of  zinc  by 
sulphuretted  hydrogen. 

Lactic  acid  is  also  produced  in  large  quantity  by  heating 
grape  or  cane  sugar  with  caustic  potash  solution  of  a  certain 
degree  of  concentration,  (B.  15,  136). 

The  relations  of  lactic  acid  to  the  sugar  varieties  appear  at  a 
superficial  glance  to  be  very  simple ;  thus  grape  sugar,  CgHigOg,  and 
lactic  acid,  CsHgOg,  are  polymers. 

Properties,  The  acid  has  not  been  obtained  free  from 
water.  When  its  solution  is  evaporated  in  an  exsiccator,  a 
thick,  non-crystallizing  and  hygroscopic  syrup  is  got, 
which  is  miscible  with  water,  alcohol  and  ether,  and  which 
gradually  gives  up  water,  with  the  formation  of  (solid)  lactic 
anhydride,  CqR-^qO^,  before  all  the  water  of  solution  has  been 
got  rid  of.  When  heated,  it  partly  goes  into  the  anhydride, 
lactide,  CgHgO^,  and  partly  breaks  up  into  aldehyde,  CO,  and 
H2O.  Similarly  it  decomposes  into  aldehyde  and  formic  acid 
upon  heating  with  dilute  sulphuric  acid  to  130°,  concentrated 
sulphuric  giving  rise  to  carbon  monoxide  instead  of  formic 
acid ; 

CH3— CH(OH)— CO2H  +  H2O  =  CH3— CHO  +  HCO2H. 
Upon  oxidation  it  yields  acetic  and  carbonic  acids ;  hydro- 
bromic  acid  converts  it  into  a-bromo-propionic  acid,  and  boiling 
with  hydriodic  acid  into  propionic  acid  itself. 

Calcium  lactate,  (CgHgOajgCa  +  SHgO  :  warty  masses  of  microscopic 
rhombic  needles.  Zinc  lactate,  (CsHgOgjgZn  +  SHgO  :  glancing  needles. 
Ferrous  lactate,  (C3HgO;3)2-f-3H20  :  bright  yellow  needles;  both  the 
ferrous  and  zinc  salts  are  used  in  medicine.  When  sodium  lactate  is 
heated  with  sodium,  Di-sodium  lactate,  CH3— CH(ONa) — C02Na,  which 
is  at  the  same  time  a  salt  and  an  alcoholate,  is  formed. 


216 


IX.  POLYATOMIC  MONOBASIC  ACIDS. 


The  Derivatives  of  lactic  acid  are  derivatives  of  it  either 
as  acid  or  as  alcohol,  and  are  perfectly  analogous  to  those  of 
glycollic  acid,  (see  table,  p.  211).  Thus  Ethyl-lactic  acid, 
CH3— CH(0C2H,)— CO2H,  a  thick  acid  liquid  which  boils 
almost  without  decomposition,"^  corresponds  to  ethyl-glycollic 
acid;  Ethyl  lactate,  which  can  be  distilled  without  decomposi- 
tion, to  ethyl  glycollate;  Lactamide,CH3— CH(OH)— CO.NH2, 
to  glycollamide,  and  Alanine,  CH3— CH(NH2)— CO.OH,  to 
glycocoU.  Alanine  results  from  the  action  of  hydrocyanic 
acid  upon  aldehyde  ammonia  (see  p.  213),  and  forms  hard 
needles  of  a  sweetish  taste. 

By  the  action  of  PCI5,  lactyl  chloride,  CH3— CHCl-  CO.Cl, 
(p.  178)  is  formed;  as  the  chloride  of  a-chloro-propionic  acid 
it  yields  the  latter  acid  and  HCl  with  water.  The  acid  just 
named  is  therefore  to  be  regarded  as  the  hydrochloric  ether 
of  lactic  acid. 

The  following  anhydrides  of  lactic  acid  are  known  : 
1.  Lactylic  acid  or  Lactic  anhydride,  CgHjoOg,  which  is  analogous  to 
glycollic  anhydride,  and  forms  a  yellow  amorphous  mass  ;  2.  Lactide, 
C6H8O4,  analogous  to  glycolide,  (tables,  M.  Pt.  125°)  ;  3.  Di-lactic  acid, 
C^jHiqCq,  the  alcoholic  anhydride,  analogous  to  di-glycollic  acid. 

2.  Ethylene-lactic  acid,  hydracrylic  acid,  CH2(OH)-CH2-CO.OH, 
( TVislicenuSy  A.  128,  1 ),  forms  a  syrupy  mass.  It  differs  from 
lactic  acid  :  (a)  By  its  behaviour  upon  oxidation,  yielding 
carbonic  and  oxalic  acids,  and  not  acetic ;  (b)  By  not  yielding 
an  anhydride  when  heated,  but  by  breaking  up  into  water  and 
acrylic  acid,  hence  the  name  hydracrylic  acid : 

CH2(OH)~CH2— COOH  =  CH2--CH— COOH  +  H^O ; 

(c)  In  solubility,  and  in  the  amount  of  water  of  crystallization 
of  its  salts,  (e.g.  zinc  salt  :  -}-  ^HgO,  very  easily  soluble  in 
water ;  calcium  salt  :   +  2H2O). 

3.  Sarco-lactic  acid,  pam-ladic  acid,  active  lactic  acid, 
CH3— CH(OH)— CO2H,  (Liebig),    This  occurs  in  the  juice  of 

*  By  the  entrance  of  the  ethylic  group,  the  hydroxy  1  is  in  a  certain 
degree  paralysed  as  regards  its  action,  in  consequence  of  which  ethyl- 
lactic  acid  resembles  propionic  acid  much  more  nearly  than  lactic  acid 
itself  does. 


HOMOLOGUES  OF  LACTIC  ACID. 


217 


flesh,  and  results  instead  of  ordinary  lactic  acid  in  certain 
fermentations.  Its  properties  are  almost  identical  with  those 
of  the  latter,  for  instance,  it  possesses  an  equal  facility  in 
forming  lactide  or  aldehyde.  It  is  however  optically  active 
(dextro-rotatory),  and  its  salts  also  differ  somewhat  from 
those  of  the  isomeric  acid  ;  thus  the  zinc  salt :  +  SHgO,  is 
much  more  easily  soluble,  and  the  calcium  salt :  +  4H2O, 
much  more  difficultly  soluble  than  the  corresponding  common 
lactates. 

The  isomerism  of  para-lactic  acid  and  the  lactic  acid  of 
fermentation  can  hardly  depend  upon  a  difference  of  consti- 
tution, since  their  chemical  behaviour  is  the  same,  but  arises 
most  probably  from  physical  grounds.  This  kind  of  isomerism 
is  therefore  termed  physical  isomerism."  Either  modifica- 
tion can  be  converted  into  the  other;  thus,  common  lactic  acid 
becomes  optically  active  ( + )  by  the  action  of  fission  fungus, 
(Penicillium).  For  further  details,  see  p.  32  and  under  tartaric 
acid. 

Oxy-butyric  acids,  (see  p.  208). 

/3-0xy-"butyric  acid,  CH3— CH(OH)— CH2— COgH,  a  syrup,  is  related 
to  aldol  and  aceto-acetic  acid.  An  optically  active  ( — )  modification  is 
contained  in  diabetic  urine  and  blood. 

7- Oxy -"butyric  acid,  CH2(0H)— CHg — CHg — COgH,  is  only  capable  of 
existence  in  its  salts  and  not  in  the  free  state,  as  it  breaks  up  into 
water  and  its  lactone,  butyro-lactone. 

a-Oxy-isobutyric  acid,  (CH3)2=C(OH)— CO2H,  (Wurtz),  results  from 
acetone  cyanhydrin  (p.  142),  and  is  therefore  also  called  acetonic  acid. 

Amido-butyric  acids  are  known,  e.g.  Piperic  acid,  C3Hg(NH2)(C02H). 

Oxy-valeric  acids.  Several  amido-valeric  acids  have  been  prepared 
synthetically,  while  others  have  been  obtained  by  the  decomposition  of 
albumen  and  of  conine  and  piperidine  derivatives,  and  have  also  been 
found  in  the  pancreas  of  the  ox. 

Oxy-caproic  acids.     Leucine  or  a-Amido-caproic  acid, 

CH3— CH2— CH2— CH2— CH(NH2)— CO2H,  is  a  derivative  of 
a-oxy-caproic  or  leucic  acid  (Strecker) ;  it  forms  fatty  glancing 
plates  and,  like  other  amido-acids,  is  nearly  related  to  albumen. 
It  is  found  in  old  cheese,  also  abundantly  in  the  animal  organ- 
ism in  the  gastric  salivary  gland,  and  in  the  shoots  of  the 
vetch  and  gourd,  etc.    It  forms,  along  with  tyrosine,  a  con- 


218 


IX.  POLYATOMIC  MONOBASIC  ACIDS. 


stant  product  of  the  digestion  of  albumen  in  the  small  intestine 
and  of  the  decay  of  albuminous  substances,  and  results  from 
the  latter  by  boiling  them  with  alkalies  or  acids.  It  also 
appears  to  have  been  prepared  syntheticall}^  It  closely  re- 
sembles glycocoll,  and  forms  a  characteristic  sparingly  soluble 
blue  copper  salt.  Leucine  is  dextro-rotatory,  a  laevo-rotatory 
modification  being  also  known  (B.  19,  Kef.  567). 

Conic  acid,  C7H15NO2,  and  Homo-conic  acid,  C8H17NO2,  are  higher 
homologiies  of  leucine  which  have  been  prepared  from  conine. 

Oxy-stearic  acid,  CigHggOg,  is  obtained  by  the  action  of  cold  cone. 
H2SO4  on  oleic  acid — (addition  of  H^O) — and  forms  a  white  mass.  Its 
sulphuric  ether  or  Oxy-stearo- sulphuric  acid,  CigHggOglOSOgH),  is  of 
importance  for  the  manufacture  of  Turkey  red. 

Coccerylic  acid,  C3iHg203,  occurs  in  cochineal  wax,  combined  with 
cocceryl  alcohol. 

The  two  following  are  diatomic  monobasic  acids  :  Ricinoleic  acid, 
C18H34O3  from  castor  oil,  and  its  isomer,  Rapinic  acid,  C18H34O3,  from 
rape  seed  oil. 

Appendix.  Lactones.  The  7-oxy-acids  (see  7-oxy-butyric  acid)  are 
very  unstable  in  the  free  state,  so  that  when  an  acid  is  added  to  their 
salts,  not  the  oxy-acids  themselves  but  anhydrides  are  obtained,  e.g. 
butyro-lactone,  (see  p.  209)  : 

CH2(0H)— CH2— CH2— CO.OH  =  CH2— CHg— CH2— CO  +  HgO. 

6  ^1 

These  lactones  are  to  be  regarded  as  intramolecular  anhydrides  {i.e. 
1  mol.  acid  - 1  mol.  HgO),  or  ethers,  the  acid  part  of  the  molecule 
etherifying  in  some  degree  the  alcoholic  part. 

The  lactones  of  the  7-oxy-acids,  *' 7-lactones,"  are  for  the  most  part 
neutral  liquids  of  faint  aromatic  odour,  easily  soluble  in  alcohol  and 
ether,  and  distilling  without  decomposition.  They  dissolve  in  alkalies 
to  the  salts  of  the  corresponding  oxy-acids,  and  form  brominated  fatty 
acids  with  HBr,  and  amido-acids  with  NH3. 

5-  and  j8-,  but  only  a  few  a-lactones,  from  5-,  and  a-oxy-acids,  are 
also  known.  They  show  marked  differences  in  the  ease  with  which 
they  are  formed  and  in  their  stability,  the  7-lactones  being  the  most 
stable. 

The  formation  of  lactones  by  warming  the  unsaturated  acids, 
CnH2n-2  02,  which  are  isomeric  with  them,  with  HBr  or  with  moder- 
ately concentrated  H2SO4,  is  worthy  of  note. 

For  details,  see  Fittig  and  his  pupils,  A.  208,  37,  111 ;  216,  26,  etc. 


TRI-  TO  HEXATOMIC  ACIDS. 

B.  Tri-  to  hexatomic  monobasic  Acids. 


Summary, 


Name  and  Formula. 

Preparation. 

Remarks. 

A.  Triatomic 
monobasic 
acids. 

(Di-oxy- propionic 

acid) 
C^HslOHj^lCO^H). 
Glyceric  acid. 

1.  inactive ; 

2.  optically  active. 

From  glycer- 
ine. 

Alcoholic  amine;  Serine, 
C2H3(OH)(NH2)(C02H) 
from    silk-gum  and 
dilute  H2SO4;  analo- 
gous to  glycocoU. 

B.  Tetratomic 
monobasic 
acids. 

(Tri-oxy-butyric 

acid) 
C3H4(OH)3(C02H). 
Erythritic  acid. 

Fromerythrite; 

from  Isevulose 

with 
Ba(OH)2  +  HgO 

C.  Pentatomic 
monobasic 
acids. 

(Tetr-oxy-caproic 

acids) 
C5H,(OH)4(C02H). 
1  1.  Saccharic  acid  ; 
2  and  3.  Iso-  and 
Meta-saccharic 
acids. 

1.  From  grape 
and  fruit 
sugars  with 

,  CaO  ;  2  and 
3.  from  milk 
sugar  in  the 
same  way. 

Known  as  salts  and  as 
lactones,   e.g.  Sacch- 
arine,   CgHioOg  (iso- 
meric    with  starch), 
which  crystallize  well. 

D.  Hexatomic 
monobasic 
acids. 

(Pent-oxy-caproic 

acids) 
C5He(OH)5(C02H). 

1.  iVianuiulV/  ctt-iu.  y 

2.  Gluconic  acid  ; 

3.  Galactonic  acid. 

1.  From  man- 
nite;  2.  from 
dextrose, 
cane  sugar, 
etc. ,  with 
brom.  water 
and  AggO  ; 
3.  from  milk 
sugar  in  an 
analogous 
manner. 

The  constitution  of  the  saccharic  acids,  etc. ,  is  of  importance  on  account 
of  the  deductions  which  can  be  drawn  from  it  with  regard  to  the 
constitution  of  the  sugars.    (Cf.  B.  17,  1302  ;  18,  2514.) 

Just  as  the  glycols  yield  in  the  first  instance  diatomic 
monobasic  acids  upon  oxidation,  compounds  which  possess  at 


220 


IX.  POLYATOMIC  MONOBASIC  ACIDS. 


the  same  time  the  characters  of  a  monatomic  alcohol  and  a 
monobasic  acid,  so  are  the  polyatomic  alcohols  at  first  con- 
verted (by  cautious  oxidation  in  the  air  in  presence  of  platinum 
black,  or  also  by  means  of  nitric  acid),  into  monobasic  acids, 
which  likewise  retain  the  characteristics  of  a  mono-,  di-,  tri-, 
etc.  atomic  alcohol,  i.e.,  into  tri-,  etc.  atomic  monobasic  acids. 
These  correspond  entirely  with  lactic  acid  in  behaviour,  but,  as 
alcohols,  are  polyatomic. 

Since  the  oxidation  consists  in  the  conversion  of  a  — CH2.OH 
group  into  carboxyl,  the  resulting  acids  consequently  contain  as 
many  hydroxyls  as  the  original  alcohols,  this  number  being  again  ex- 
pressed by  the  designation  **tri-,  tetra-,  etc.  atomic  monobasic  acids." 
The  number  of  alcoholic  hydroxyls  in  the  molecule  is  determined — as  in 
the  case  of  the  polyatomic  alcohols — by  the  number  of  acetyl  groups 
which  can  be  introduced  upon  treatment  with  acetic  anhydride. 

The  law  which  applies  to  the  polyatomic  alcohols,  viz.,  that 
only  one  hydroxyl  can  be  bound  to  one  atom  of  carbon,  also 
holds  good  for  the  alcohol-acids.  Their  carbon-atom  chain  is 
the  same  as  that  of  the  mother  compound. 

Most  of  the  compounds  belonging  to  this  class  either 
crystallize  badly  or  are  gum-like.  A  number  of  these  acids 
also  result  from  the  cautious  oxidation  of  the  sugars  or  of  the 
unsaturated  acids,  CnH2n-202,  (see  p.  164). 

0.  Aldehyde -alcohols. 

1.  GlycoUic  aldehyde,  CH2(0H)— CHO.  This  is  only  known  in 
aqueous  solution. 

2.  Aldol,  CH3— CH(OH)— CH2— CHO.  A  condensation  product  of 
aldehyde,  see  p.  134  (  Wurtz),  It  forms  a  thick  liquid,  easily  soluble  in 
water. 

3.  Glyceric  aldehyde,  0H2(0H)— CH(OH)— CHO,  is  the  aldehyde  of 
glyceric  acid,  and  is  obtained  by  very  careful  oxidation  of  glycerine. 
It  is  only  known  in  solution.  It  acts  as  a  powerful  reducing  agent,  and 
is  changed  into  a  sugar  by  condensation.    (See  acrose.) 

4.  Arabinose,  C5H10O5,  =  CH2.OH— (CH.0H)3— CHO,  is  produced 
by  boiling  gum  arable  with  dilute  sulphuric  acid,  and  forms  dextro- 
rotatory prisms.  For  its  constitution  see  Kiliani,  B.  20,  339,  1233. 
It  was  formerly  reckoned  among  the  glucoses. 


KETONE-ALCOHOLS,  ETC.  221 

The  Sugars  are  also  to  be  looked  upon  as  aldehyde-alcohols 
or  ketone-alcohols;  they  will  be  treated  of  separately  (p.  28o). 

D.  Ketone-alcohols. 

Acetone-alcohol,  acetol,  acetyUarUnol.  CH3-C0-CH,0H  Only 
known  in  aqueous  solution.  Is  prepared  from  ^l-^^"^]^^^^^^^  "f, 
AgoO,  and  by  fusing  grape  sugar,  etc.,  with  potash,  (B.  16,  837).  it 
reduces  Fehling's  solution  even  in  the  cold. 

E.  Diatomic  Aldehydes. 

Glyoxal,  CHO-CHO,  {Delus,  1856).  Formed  by  the 
cautious  oxidation  of  alcohol  or,  better,  of  aldehyde.  White 
deliquescent  mass.  Possesses  all  the  characteristic  properties 
of  aldehydes ;  being  a  diatomic  aldehyde,  its  bisulphite  results 
from  1  mol.  glyoxal  and  2  mols.  NaHSOg. 

Concentrated  ammonia  converts  it  into  Glyoxaline,  C3H4N2,  a  strong 
base,  of  a  faintly  fish-like  odour,  having  probably  the  constitution : 
CH-N   >\  ^.^^^^  interesting  derivatives,  e.g.,  Oxal-ethyline, 

CH— NH/ 

CH-N         \^__^^^^  a  base  of  alkaloid  nature  and  of  strongly 

CH-Nie^Hg)/  .    -R  p^in 

poisonous  properties,  (Wallach,  A.  184,  1 ;  13.  13, 

F.  Diatomic  Ketones.   (See  also  p.  177.) 

1.  Di-acetyl,  di-keto-hutane,  CH3-CO-CO-CH3.  J^is  can  be  pre- 
pared  by  treating  iso-nitroso-methyl  acetone,  CH3-CH(N.OH)-bU-un3 
(which  results  from  the  action  of  HNO^  on  methyl  aceto-acetic  ether) 
with  NaHSOg,  and  subsequently  boiling  with  dilute  H2SO4.  Yellow- 
green  liquid  of  quinone  odour,  its  vapour  having  the  colour  of  chlorme. 

B.  pt.  sr-ss\ 

2.  Acetyl-acetone,  CH3-CO-CH,-CO-CH3,  is  formed  by  the 
action  of  AlaClg  upon  acetyl  chloride  {Combes). 

3.  Acetonyl-acetone,  di-keto-hexane,  CH3— CO-CH,— CH,-CO  ^CE., 
Prepared  from  monochlor-acetone  and  aceto-acetic  ether,  (p.  226;  B.  17. 

2756). 


222 


IX.  POLYATOMIC  MONOBASIC  ACIDS. 


These  three  compounds  are  the  simplest  representatives  of  the 
interesting  class  of  di-ketones.  They  are  distinguished  as  a,  /3, 
and  7,  (1:2,  1 : 3,  and  1  : 4)  di-ketones  according  as  the  carbonyl  groups 
are  close  together,  ( — CO — CO — ),  or  separated  by  one  carbon  atom, 
(_C0— CH2~C0-),  or  by  two,  (— CO— CH^-CHg— CO— ).  They 
show  the  most  varying  behaviour  as  regards  condensation  with  ammonia, 
phenyl-hydrazine,  etc.,  and  are  therefore  of  value  for  the  synthesis  of 
the  derivatives  of  quinoline  (from  of  pyrazol  (from  of  furfurane 
and  pyrrol  (from  7-),  and  of  benzene  (from  a-di-ketones).  Their  con- 
stitution frequently  follows  directly  from  their  modes  of  formation. 

G.  Ketone-aldehydes. 

We  have  also  become  acquainted  recently  with  ketonic-aldehydes, 
e.g.— 

Aceto-acetic  aldehyde,  CH3 — CO — CH2 — CHO,  the  aldehyde  of  aceto- 
acetic  acid,  which  results  from  the  condensation  "  of  acetone  and  ethyl 
formate  under  the  influence  of  sodium  ethylate ;  it  is,  however,  incap- 
able of  existence  in  the  free  state.    (See  p.  226  ;  also  B.  21,  1144.) 

H.  Monobasic  Aldehyde-acids. 

0^yoxdi\iQd^GiA,glyoxylicadd,  CHO-C02H,(orCH(OH)2-C02H), 
occurs  in  unripe  fruits  such  as  grapes,  gooseberries,  etc., 
and  may  be  prepared,  e.g,^  by  superheating  dichlor-acetic 
acid,  CHCI2 — COgH,  with  water,  CI2  being  here  exchanged 
for  0  or  2 (OH).  It  crystallizes  in  rhombic  prisms,  easily 
soluble  in  water,  and  is  volatile  with  steam.  The  acid  and 
most  of  its  salts  contain  1  mol.  HgO,  which  points  to  the 
formula  CH(0H2) — COgH,  analogous  to  that  of  chloral  hydrate, 
from  which  it  is  derivable  by  the  exchange  of  3C1  for  0  and 
OH. 

Formyl-acet/ic  acid,  CHO — CHg — COgH,  which  is  at  the  same  time 
the  semi-aldehyde  of  malonic  acid,  is  formed  as  ether  by  the  action  of 
sodium  upon  a  mixture  of  ethyl  formate  and  acetate  (see  p.  226).  It  is 
readily  condensible  to  trimesic  acid  (p.  430). 

I.  Monobasic  Ketonic  acids. 

Ketonic  acids  are  compounds  which  possess  at  one  and  the 


MONOBASIC  KKTONIC  ACIDS. 


223 


same  time  the  properties  of  acids  and  ketones;  thus,  besides 
being  capable  of  forming  salts,  ethers,  etc.,  they  also  combine 
with  sodium  bisulphite,  yield  oximes  with  hydroxylamme 
hydrochlorate  (see  p.  142),  are  reduced  by  nascent  hydrogen 
to  secondary  ,  alcohol-acids,  and  so  on.  The  most  important 
members  of  this  class  are  pyroracemic  acid,  CH3— CO— CO2H, 
aceto-acetic  acid,  CH3-C0-0H,-C0,H,  and  levulinic  acid, 
CH3-CO-OH2-~CH2-C02H. 

Constitution  and  Nomenclature.  The  ketonic  acids  are  charac- 
terized theoretically  by  the  presence  of  carboxyl  and  of  car- 
bonyl,  the  latter  being  linked  to  carbon  on  both  sides.  They 
may  be  derived  from  the  monobasic  fatty  acids  in  such  manner 
that  one  hydrogen  atom  of  the  radicle  of  the  latter  is  replaced 
by  an  acid  radicle  R— CO— ,  (in  the  cases  above  mentioned  by 
CH  —CO,  acetyl)—,  as  the  name  aceto-acetic  acid  indicates. 
Levulinic 'acid  is  therefore  /5-aceto-propionic  acid,  and  pyro- 
racemic acid  is  acetyl-formic  acid;  or,  the  ketonic  acids  are 
derived  from  the  fatty  acids  by  the  replacement  of  the  two 
hydrogen  atoms  of  a  CHg—  group  by  an  atom  of  oxygen. 

The  position  of  the  oxygen  atom  may  therefore  be  indicated  by  the 
prefixes  a,  /3,  and  7,  etc.,  as  in  the  case  of  the  oxy-acids  (p.  208),  and 
the  haloid  substitution  acids.  Pyroracemic  acid  is  thus  a-keto-propionic 
acid,  aceto-acetic  acid  is  jS-keto-butyric  acid,  and  levulinic  acid  is 
7-keto-normal-valeric  acid.     (Cf.  Baeyer,  B.  19,  160.) 

The  constitution  of  the  ketonic  acids  is  as  a  rule  easy  to  determine, 
either  from  the  mode  of  their  synthesis,  or  from  their  transformation  into 
the  corresponding  alcohol-acids- (oxy-acids)— of  known  constitution, 
by  means  of  nascent  hydrogen,  and  so  on.  For  the  constitution  of 
aceto-acetic  acid  see  also  p.  227. 

While  the  a-  and  7-ketonic  acids  are  stable  liquids,  some  of  which 
may  even  be  distilled,  the  jS-ketonic  acids  are  very  unstable  in  the  free 
state  and  break  up  very  readily  into  COg  and  the  corresponding  ketone. 

Pyroracemic  acid,  C3H4O3,  =  CH3— CO  -CO^H,  is  a  liquid 
which  is  readily  soluble  in  water,  alcohol  and  ether,  boils  with 
slight  decomposition  at  165°-170°,  and  smells  of  acetic  acid 
and  extract  of  beef. 

Formation.  1.  By  the  dry  distillation  either  of  tartaric  or 
of  racemic  acid,  hence  its  name. 


224 


IX.  POLYATOMIC  MONOBASIC  ACIDS. 


2.  By  the  oxidation  of  lactic  acid  by  means  of  KMn04. 

3.  By  saponifying  acetyl  cyanide  with  HOI,  {Claisen,  Shadwell) ; 

CH3— CO— CN  +  2H2O  =  OH3— CO— CO2H  +  NH3. 

Pyroracemic  acid  has  a  tendency  to  polymerize.  Its 
salts  crystallize  only  with  difficulty.  Nascent  hydrogen 
reduces  it  to  ethylidene-lactic  acid :  CH3 — CO^ — COgH  +  H2,  = 
CH3 — CH(OH) — COgH,  from  which  reaction  and  from  mode  of. 
formation  3,  its  constitution  follows.  It  possesses  in  a  marked 
degree  the  ketonic  property  of  forming  condensation  products, 
going  either  into  derivatives  of  benzene,  (B.  5,  956),  or — in 
presence  of  ammonia — into  those  of  pyridine.  Sulphuric 
acid  causes  it  to  condense  with  the  aromatic  hydrocarbons, 
just  as  in  the  case  of  the  ketones,  (B.  14,  1595). 

Cystine,  0^11^2^2^204'  disulphide  of  amido-thio-lactic 
acid  or  cysteine,  C2H3(NH2)(SH)C02H,  is  to  be  regarded  as  a 
derivative  of  pyroracemic  acid,  (see  ethyl  di-sulphide).  It 
is  found  in  urinary  sediments  and  gravel,  (B.  18,  258). 

a-Keto-but3rric  aciCi, propionyl-carboxylic  acid,  CH3 — CHg — CO — COgH, 
resembles  pyroracemic  acid. 

Aceto-acetic  acid,  /S-keto-butyricacid,  CII3 — CO — OH2 — OOgH. 
A  strongly  acid  liquid,  miscible  with  water,  and  breaking  up 
into  acetone  and  carbonic  acid  upon  warming.  It  is  prepared 
by  the  cautious  saponification  of  its  ethyl  ether,  (B.  15,  1376  ; 
1871).  Its  aqueous  solution  is  coloured  violet-red  by  ferric 
chloride.  The  Na-  or  Oa-salt  is  sometimes  contained  in 
urine,  (B.  16,  2314).  Aceto-acetic  acid  may  also  be  looked 
upon  as  acetone-carboxylic  acid,  03H50(002H). 

Aceto-acetic  ether,  OH3 — 00 — OH2 — OO2O2H5,  is  obtained 
in  the  form  of  its  sodium  compound,  sodio-aceto-acetic  ether, 
by  the  action  of  sodium  upon  ethyl  acetate,  {Geuther,  1863; 
Frankland  and  Duppa) : 

2OH3— OO.OC2H5  -1-  Na 

=  OH3— 00— OHNa— OO.OO2H5  +  02H,0H  +  H. 

According  to  Claisen  (B.  20,  651),  there  is  first  formed  in  this 
reaction  some  sodium  ethylate,  C^HgONa,  by  the  decomposition  of  a 
small  portion  of  the  acetic  ether,  and  this  then  combines  with  more 


ACETO-ACETIC  ETHER. 


225 


/OC,H, 

ether  to  the  compound  CHo— Cv— OCgHg,  which  is  a  derivative  of  ortho- 

\ONa 

acetic  acid  (p.  175).  This  last  compound  now  reacts  with  a  further 
molecule  of  acetic  ether  to  yield  sodio-aceto-acetic  ether,  with  separa- 
tion of  2  mols.  alcohol,  the  alcohol  thus  separated  yielding  sodium 
ethylate  with  further  sodium,  and  so  on. 

By  this  synthesis  2  mols.  of  acetic  ether  combine  together  under  the 
influence  of  sodium  ethylate.  The  compound  ethers  homologous  with 
acetic  ether,  and  also  mixtures  of  two  different  ethers,  behave  in  the 
same  way,  thus : 

X— CO.OR  +  HX'— CO.OR   =   X— CO-X'— CO.OR  +  R.OH. 

In  like  manner  mixtures  of  ketones  or  aldehydes  with  compound  ethers 
can  be  condensed"  by  means  of  sodium  ethylate  to  ketone-aldehydes, 
di-ketones,  etc.    (Cf.  aceto-acetic  aldehyde,  p.  222. ) 

The  ether  is  obtained  from  the  sodium  compound  upon  the 
addition  of  acid.  It  is  a  liquid  of  neutral  reaction,  boiling  at 
181°,  only  slightly  soluble  in  water  but  easily  in  alcohol  and 
ether,  and  of  a  pleasant  fruity  odour.  Ferric  chloride  colours 
its  aqueous  solution  violet-red.  It  is  split  up  upon  being  boiled 
with  alkali,  dilute  aqueous  alkali  or  baryta  water  (or  also 
dilute  sulphuric  acid)  producing  mainly  carbon  dioxide, 
acetone  and  alcohol;  (^^ketonic  decomposition"): 
CH3— CO— CH2— C02(C2H5)  +  H2O 

=  CH3— CO— CH3  -t-  CO2  +  HO.C2H5; 
very  concentrated  alcoholic  potash,  however,  produces  chiefly 
(2  mols.)  acetic  acid  ;  ("acid  decomposition,"  Wislicenus) : 
CH3— CO— CH2— C02(C2H5)  +  2H2O 

=  2CH3— CO.OH  +  HO.C2H5. 

One  atom  of  hydrogen  in  aceto-acetic  ether  is  easily  replace- 
able by  metals  {Geuther ;  Conrad,  A.  188,  269).  The  sodium 
salt  results  with  evolution  of  hydrogen  upon  the  addition  of 
sodium,  and  also  upon  mixing  the  alcoholic  solution  of  the 
ether  with  the  calculated  amount  of  sodium  dissolved  in 
absolute  alcohol : 

^^"^fP^i^^^,)  +  C^H^.ONa  =  +  C^H.^.OH. 

In  agreement  with  this  the  ether  dissolves  in  dilute  alkali,  being 
again  separated  from  the  solution  by  the  addition  of  acid. 

(506  p 


226 


IX.  POLYATOMIC  MONOBASIC  ACIDS. 


Sodio-acelo  acetic  ether,  CH3— CO— CHNa— COaCgH^ ; 
long  needles  or  a  faintly  glancing  loose  white  mass.  Copper 
salt :  bright  green  needles. 

The  constitution  of  aceto-acetic  ether  follows  from  its  formation 
and  behaviour.  The  latter  shows  that  it  is  a  hydrogen  atom  of  the 
methylene  group,  CH2,  which  is  replaceable  by  metals,  this  capability 
of  replacement  being  explained  by  the  acidifying  influence  of  the  two 
carbonyl  groups  which  are  directly  bound  to  the  methylene,  viz.,  the 
CO  of  the  group  CH3— CO,  and  the  CO  of  the  group  CO. OH.  (Compare 
the  relation  of  hydrated  carbonic  acid,  C0(0H)2,  to  two  molecules  of 
water,  H(OH).) 

The  metal  in  sodio-aceto-acetic  ether  is  readily  replaced 
by  an  alcohol  radicle  by  the  action  of  iodo-  or  bromo-alkyl, 
sodium  iodide  or  bromide  being  formed  at  the  same  time. 
We  thus  obtain  alkylated  aceto-acetic  ethers,  e,g, : 

Methyl-aceto-acetic  ether  or  Ethylic  methyl-aceto-acetate, 

CH3— CO— CH(CH3)— C02(C2H5),  and  the  corresponding 
Ethyl-  and  Propyl-aceto-acetic  ethers,  etc.  In  these  com- 
pounds the  H  may  be  again  replaced  by  Na,  and  this  again 
substituted  by  alkyl,  with  the  production  of  di-alkylated  aceto- 
acetic  ethers,  e.g. :  Dimethyl-aceto-acetic  ether  or  Ethylic  di- 
me thy  1-aceto -acetate,  CH3-CO-C(CH3)2-C02(C2H5) ;  Methyl- 
ethyl-aceto-acetic  ether,  CH3-CO-C(CH3)(C2H5)-C02(C2H5), 
and  so  on. 

These  alkylated  aceto-acetic  ethers  exactly  resemble  their 
mother  substance,  especially  in  that  they  undergo  either  the 
"  ketonic  decomposition  "  or  the  "  acid  decomposition,"  accord- 
ing to  their  degree  of  concentration,  upon  treatment  with 
alkalies;  the  latter  decomposition  also  upon  treatment  with 
dilute  acids,  (see  above,  also  A.  190,  275).  The  first-named 
decomposition  leaves  the  substituting  alcohol  radicles  in  the 
acetone  residue  of  the  molecule,  and  the  last-named  in  one  of 
the  two  resulting  acid  molecules,  i.e.,  there  are  formed  either 
alkyl-acetones  (homologues  of  acetone),  or  alkyl-acetic  acids 
(homologues  of  acetic  acid).  We  have  thus  at  command  here 
a  most  excellent  method  for  the  synthesis  of  any  simple  or 
double  alkyl  ketone  or  acid ; 


DIBASIC  ACIDS. 


227 


1.  CH3— CO— CRR'— CO2C2H5  +  H2O 

=  CH3— CO— CHRR'  +  HO-C^H^  +  CO2; 

2.  CH3— CO— CRR— CO2C2H5  +  2H2O 

=  CH3— CO.OH  +  CHRR'— CO2H  +  HO.C2H5. 
(RR'  =  alcohol  radicles.  Cf.  Wislicenus  and  his  pupils,  A.  186, 
161.) 

In  a  perfectly  analogous  manner  we  can  introduce  acid  instead  of 
alkyl  radicles  into  aceto-acetic  ether,  and  thereby  give  rise  to  the  most 
various  compounds,  e.g.,  from  acetylchloride,  di-aceto-acetic  ether, 
(CH3— C0)2CH— C02(C2Hg) ;  from  chloro-carbonic  ether,  CI— CO2C2H5 
(p.  269),  acetol-malonic  ether,  (CH3— CO)— CHlCO.CsHgja ;  from 
monochlor-acetic  ether,  CH2Ci — COgtCgHg),  acetol- succinic  ether, 
CH3— CO— CH(CH2— C02C2H5)(C02C2H5),  (see  malonic  and  succinic 
acids,  and  also  the  synthesis  of  dibasic  acids),  etc.  Iodine  acts  upon 
sodio-aceto-acetic  ether  to  produce  di-acetol  succinic  ether,  which  is 
interesting  from  its  transformations,  thus  : 

CH3-CO  -CHNa-C02C2H5  CH3-CO-CH-CO2C2H5 

+  I2  =  I  +  2NaI. 

CH3-CO-CHNa-C02C2H5  CH3-CO-CH-CO2C2H5 

Chlor-  and  Dichlor-aceto-acetic  ethers,  which  are  very  active  chemi- 
cally, are  produced  by  the  replacement  of  the  H  of  the  methylene 
group  by  CI.  The  two  methylene  hydrogen  atoms  are  also  replaceable 
by  the  iso-nitroso  group,  =N — OH  (by  the  action  of  N2O3),  and  by  the 
imido  group,  =NH,  (cf.  A.  226,  294). 

In  many  reactions  aceto-acetic  ether  behaves  as  if  it  were  in  the 
first  instance  changed  into  the  isomeric  form — the  pseudo-form — 
CH3C(0H)=CH— C02(C2H5),  /3-oxy-crotonic  ether.  (See  the  furfurane 
group,  and  the  appendix  to  the  cyanogen  compounds.) 

Levulinic  acid,  CgHgOg,  =  CH3— CO— CHj— CH2— CO2H.  Plate 
crystals,  M.  Pt.  33°,  B.  Pt.  239°.  Results  from  the  action  of  acids  upon 
cane  sugar,  Isevulose,  cellulose,  gum,  starch  and  other  carbo-hydrates, 
(A.  175,  181  ;  206,  207),  and  has  also  been  prepared  synthetically. 
It  is  employed  in  cotton  printing. 


X.  DIBASIC  AOIDS. 

Dibasic  acids  are  those  which  are  capable  of  forming  two 
series  of  salts,  acid  and  neutral,  with  monatomic  bases,  and 
likewise  two  series  of  ethers,  chlorides,  amides,,  etc.  The 
dibasic  acids  proper  are  characterized  theoretically  by  the 
presence  of  two  carboxyls  in  the  molecule. 


228 


X.  DIBASIC  ACIDS. 


These  acids  may  either  possess  the  acid  character  pure  and 
simple,  or  also  at  the  same  time  the  character  of  an  alcohol, 
e.g.  lactic  acid  ;  in  the  latter  case  they  still  contain  alcoholic 
hydroxyl.  A  distinction  is  drawn  between  diatomic  dibasic 
and  tri-,  tetra-,  etc.  atomic  dibasic  acids.  They  may  be  either 
saturated  or  unsaturated  compounds.  The  dibasic  carbonic 
acid  will  be  treated  of  later  on  (pp.  266  seg^.). 


A.  Saturated  diatomic  dibasic  Acids,  CnH2n_204. 

Oxalic       acid,  CgHg  0^  Suberic  acid,  Cg  H^^O^ 

Malonic       „    C3H4  O4  Lepargylic,        „    Cg  H^gO^ 

Succinic       „    C^Hg  0^  Sebacic  „  CiQH^g04 

Pyrotartaric  „    CgHg  O4  Brassylic  „  C-^^^fi^ 

Adipic         „    C^H^oO^  Eocellic  „  G^>jR^<f}^ 

Pimelic        „    (j^jR^^O^  Dicetyl-malonic  „  Cg^HggO^ 

Oxalic  acid  is  to  be  considered  as  the  isolated  group  carboxyl, 
(C0.0H)2.  Its  homologues  are  di-carboxylic  acids  of  the  paraffins; 
thus,  malonic  is  methane-di-carboxylic  acid,  CHglCOaHjg,  etc. 

The  above  are  solid  crystalline  compounds  of  strongly  acid 
character,  and  most  of  them  are  readily  soluble  in  water. 
Upon  heating,  they  either  yield  an  anhydride  or  carbon 
dioxide  is  given  off,  (see  p.  230). 

Formation. — 1.  By  the  oxidation  of  the  di-primary  glycols. 
(See  table,  p.  205.) 

la.  By  the  oxidation  of  primary  oxy-acids  and,  generally,  of 
many  complex  compounds,  such  as  fats,  fatty  acids  and  carbo- 
hydrates. 

2.  By  the  saponification  of  the  corresponding  nitriles ;  thus, 
oxalic  acid  is  formed  from  cyanogen,  and  succinic  acid  from 
ethylene  cyanide  : 

C2N2  +  4H2O   =  +  2NH3. 

C2H,(CN)2  +  m,0  =  C,11,{G0,B),  +  2NH3. 

Since  ethylene  cyanide  is  a  glycol  derivative,  its  conversion  into 
succinic  acid  represents  the  synthesis  from  a  glycol  of  an  acid  contain- 
ing two  atoms  of  carbon  more  than  itself,  i.e.  the  exchange  of  2(0H)  for 
2(C02H),  or  the  indirect  combination  of  ethylene  with  2CO2H. 


OXALIC  ACID  SERIES. 


229 


2\  By  the  saponification  of  tlic  cyano-fatty  acids  (p.  171), 
and  consequently  of  the  haloid  fatty  acids  also.  Thus  chlor-  or 
cyan-acetic  yields  malonic  acid,  /?-iodo-  (or  cyano-)  propionic, 
common  succinic  acid,  and  a-iodo-  (or  cyano-)  propionic,  ethy- 
lidene-succinic  acid. 

A  dibasic  acid  can  therefore  be  formed  from  each  oxy-acid  by  the 
exchange  of  OH  for  CO.^H,  or  indirectly  from  a  fatty  acid  by  the 
replacement  of  H  by  COgH. 

3.  The  homologues  of  malonic  acid  can  be  prepared  from 
malonic  acid  itself  by  a  reaction  exactly  analogous  to  the  aceto- 
acetic  ether  synthesis,  (the    malonic  ether  synthesis,"  p.  233). 

3^  The  dibasic  acids  are  also  obtained  by  means  of  the 
aceto-acetic  ether  synthesis.  Acetyl-malonic  and  acetyl- 
succinic  acids,  which  have  already  been  mentioned  at  p.  227, 
yield  respectively  malonic  and  succinic  acids  by  the  separation 
of  acetyl,  ('*  acid  decomposition  "). 

4,  For  further  modes  of  preparation,  see  under  succinic 
acid. 

The  Constitution  of  the  acids  C,,H2i,_204  is  as  a  rule  very  easy 
to  determine  from  the  above-mentioned  modes  of  formation, 
especially  2  and  3.  According  to  these,  one  has  to  decide 
between  the  malonic  acids  proper,  i.e.  malonic  acid  and  its 
alkylated  derivatives  (p.  234),  whose  two  carboxyl  groups  are 
both  linked  to  one  carbon  atom  : 

CH2(C02H)2,      R— CH(C02H)2,  RR'C(C02H)2, 

and  ordinary  succinic  acid  and  its  homologues,  which  contain 
the  carboxyls  bound  to  two  different  carbon  atoms. 

The  divalent  acid  residues,  CgOg  =  oxalyl,"  C3H2O2  =  malonyl," 
and  C4H4O2  =  *'  succinyl,"  which  are  combined  with  the  two  hydroxyls, 
are  termed  the  radicles  of  the  dibasic  acids. 

Isomers. — Isomers  of  oxalic  and  malonic  acids  are  neither  theo- 
retically possible  nor  actually  known.    We  know,  however,  two 

succinic  acids,  viz.,  ^J?^""^^*?!!  and  m,—GR(GO,B),. 
— CU.Url 

The  former  corresponds  to  ethylene  chloride  and  the  latter 
to  ethylidene  chloride,  from  which  they  are  res2)eccively 


230 


X.  DIBASIC  ACIDS. 


derived  by  the  exchange  of  two  chlorine  atoms  for  two  car- 
boxyls.  Hence  the  names,  ethylene-  and  ethylidene-succinic 
acids. 

Since  ethylene  cyanide  can  be  prepared  from  the  chloride,  the  above 
derivation  of  ethylene-succinic  acid  is  also  an  experimental  one ;  this  is 
not  the  case  however  with  the  isomeric  acid,  since,  speaking  generally, 
when  several  chlorine  atoms  are  bound  to  the  same  carbon  atom,  as  in 
ethylidene  chloride,  they  cannot  be  exchanged  for  cyanogen. 

Behaviour. — Those  of  the  dibasic  acids  whose  carboxyls  are 
attached  to  different  carbon  atoms  yield  intra-molecular 
anhydrides  by  the  separation  of  a  molecule  of  water.  These 
anhydrides  result  in  part  by  direct  heating,  in  part  by  the 
action  of  phosphorus  pentachloride,  acetyl  chloride  or  carbon 
oxy-chloride  upon  the  acids,  (B.  10,  1881  ;  17,  1285).  They 
recombine  slowly  with  water  to  the  hydrates. 

The  "  malonic  acids,"  on  the  other  hand,  lose  COg  on  being 
heated,  and  yield  monobasic  fatty  acids,  malonic  acid  itself 
giving  acetic  acid.  Similarly  oxalic  acid  breaks  up  into  CO2 
and  formic  acid.  (Compare  the  analogous  formation  of  CH^ 
from  CH3 — COgH.)  The  derivatives  of  the  dibasic  acids,  i.e. 
their  ethers,  amides,  etc.,  show  precisely  the  same  character- 
istics as  the  analogous  derivatives  of  the  monobasic  acids, 
especially  in  the  readiness  with  which  they  are  saponified. 


Summary. 


Derivatives. 

Salts. 

Ethers. 

Chlorides. 

Amides. 

Acid. 

Acid  sodium 
oxalate. 

^2<^2|0H 

Ethyl-oxalic 
acid. 

^2^H0(H) 
(only  known  in 
derivatives). 

^2^4  OH 
Oxamic  acid. 

Neutral. 

^2^40Na 
Neutral  sodium 
oxalate. 

Oxalic  ether. 

C4H4O2IQJ 

Succinyl 
chloride. 

^2^^2|nH2 

Oxamide. 

OXALIC  ACID. 


231 


As  in  the  case  of  tlie  glycols,  complications  only  ensue  here 
either  where  mixed  derivatives  exist,  such  e.g.  as  are  partly 
ether  and  partly  amide  (as  in  the  case  of  ethyl  oxamate,  p. 
233),  or  on  account  of  many  of  the  acids  being  capable  of 
forming  imides. 

Such  imides  are  derived  from  the  hydrogen-ammonium  salts 
of  the  acids  by  the  elimination  of  two  molecules  of  water, 
thus : 

^A<gaoS     NH3  -  2H,0   =  C,H,<S>NH. 

'  '  '  ^  r> — \  ' 

Succinic  acid.  Succinimide. 

Like  the  amides  they  are  easily  saponifiable,  (cf.  succini- 
mide). 


Oxalic  acid,  acidwn  oxalicum,  C2H2O4  +  2H2O.  This  acid 
has  been  known  for  a  very  long  time ;  it  was  investigated  by 
Scheele. 

Occurrence.  In  many  plants,  especially  in  oxalis  acetosella 
(wood  sorrel),  as  KHC2O4  in  varieties  of  Eumex,  free  in 
varieties  of  Boletus,  as  Na2C204  in  varieties  of  Salicornia,  and 
as  calcium  salt  in  rhubarb  root,  etc. 

Formation.    (See  also  p.  228) : 

1.  By  the  direct  combination  of  carbon  dioxide  with  sodium 
at  360° :  2CO2  +  Na2  =  C204Na2. 

2.  By  raising  sodium  formate  quickly  to  a  high  temperature: 

2HC02Na  =       +  Cfi^^^. 

3.  By  the  oxidation  of  sugar,  starch,  etc.,  with  HNO3,  or 
by  fusing  cellulose  with  the  hydrates  of  potash  and  soda. 
This  last  method  is  followed  for  its  preparation  on  a  large 
scale. 

The  frequency  of  its  formation  in  processes  of  oxidation  is  explained 
by  its  close  relation  to  carbonic  acid,  which  is  the  final  product  of  all 
oxidations. 


232 


X.  DIBASIC  ACIDS. 


Properties.  Fine  transparent  monoclinic  prisms  which 
effloresce  in  the  air.  Easily  sohible  in  water  and  moderately 
in  alcohol.  The  anhydrous  acid,  which  is  obtained  at  100°, 
can  be  sublimed,  but  it  decomposes  upon  rapid  heating  into 
carbon  dioxide  and  formic  acid,  or  into  carbon  dioxide,  carbon 
monoxide  and  water.  The  latter  decomposition  also  takes 
place  upon  heating  with  concentrated  sulphuric  acid : 

=  CO2  +  CO  +  H2O. 

Oxalic  acid  is  stable  as  regards  nitric  acid  and  chlorine,  but 
permanganate  of  potash  or  manganese  dioxide  in  acid  solution 
oxidizes  it  to  carbonic  acid  : 

C^H^O^  +  O  =  2CO2  +  H2O. 

Salts  and  Derivatives,  The  alkaline  salts,  acid  and  neutral, 
are  readily  soluble  in  water,  the  normal  sodium  salt  being  the 
least  so.  The  "salt  of  sorrel"  of  commerce  is  a  mixture  of 
C2O4HK  and  a  per-salt,  CsOJiK  +  CgO^Hg  +  2H2O,  (cf.  p. 
157). 

The  calcium  salt,  CgO^Ca  +  H2O  (or  SH^O),  is  insoluble  in 
water  and  acetic  acid,  and  serves  for  the  recognition  of  oxalic 
acid. 

Ferro-potassic  oxalate,  (C20^)2FeK2  +  H20,  finds  apphcation  in  photo- 
graphy as  a  powerful  reducing  agent. 

Antimonic  oxalate  is,  like  tartar  emetic,  employed  as  a  mordant  in 
dyeing. 

Ethyl  oxalate,  oxalic  ether,  0204(02115)2,  which  can  be  directly  pre- 
pared from  its  components,  is  liquid,  while  Methyl  oxalate,  0204(0113)2, 
is  solid,  crystallizing  in  plates  which  melt  at  51° ;  both  of  them  possess 
an  aromatic  odour,  distil  without  decomposition,  and  are  easily  saponi- 
fiable.  Partial  saponification  (with  one  mol.  KOH  in  alcoholic  solution) 
produces  e.g.  Potassium  ethyl-oxalate,  0204(02H5)K,  from  which  the 
free  Ethyl-oxalic  acid,  0304(02115)11,  which  is  readily  saponifiable,  and 
its  chloride,  Ethyl-oxalyl  chloride,  002(02115) — 0001,  can  easily  be  pre- 
pared. The  normal  chloride  of  oxalic  acid,  O2O2OI2,  does  not  exist. 
Oxalic  ether  yields,  with  two  mols.  NH3,  oxamide,  and  with  one  mol. , 
the  mixed  derivative  oxamic  acid,  analogously  to  mode  of  formation  4  of 
the  amides  (p.  180). 

Oxamide,  C202(NH2)2,  the  normal  amide  of  oxalic  acid,  is  obtained, 
among  other  methods,  by  the  distillation  of  ammonium  oxalate  (cf.  p. 
180),  by  the  partial  saponification  of  cyanogen,  and  by  the  action  of 


MALONIC  ACID. 


233 


bydrogen  dioxide,  HgOg,  upon  hydrocyanic  acid,  (B.  18,  355).  It  is  a 
white  crystalline  powder.  As  an  amide  it  is  easily  saponifiable,  and 
convertible  into  cyanogen  by  the  abstraction  of  HgO,  etc. 

Oxamic  acid,  C202(NH2)(OH),  the  acid  amide  or  aminic  acid  of  oxalic 
acid,  results  from  the  heating  of  acid  oxalate  of  ammonia.  It  is  a 
crystalline  powder,  difficultly  soluble  in  cold  water. 

Ethyl  oxamate,  oxamethane,  COlNHs) — CO.OCgHg,  (see  above). 
Corresponding  to  oxamide  we  have  Di-methyl-oxamide,  COlNHCHg)— 
C0(NHCH3),  and  corresponding  to  oxamethane,  Ethyl-dimethyl-oxamate, 
CO(N[CH3]2)— CO.OC2H5,  both  already  mentioned  at  p.  113.  PCI5 
converts  oxamethane  into  Cyano- carbonic  ether,  CN — CO.OC.^Hg,  a 
liquid  of  pungent  odour,  which  is  to  be  regarded  as  a  semi-nitrile  of 
oxalic  acid. 

Amide-  and  Imido- chlorides  of  oxalic  acid  are  also  known. 
CO 

Oximide,    |    ^NH,  is  got  by  the  action  of  PCL  upon  oxamic  acid, 
CO"^ 

and  forms  colourless  prisms  easily  soluble  in  water  and  of  neutral 
reaction.  It  is  quickly  saponified  by  hot  water,  and  transformed  into 
oxamide  by  ammonia,  (B.  19,  3228). 

Malonic  acid,  C3H4O4,  =  CH2(C02H)2. 
Occurrence.    In  beetroot. 

Formation.  (1)  By  the  oxidation  of  malic  acid  by  means  of 
chromic  acid,  hence  its  name ;  (2)  by  the  saponification  of 
malonyl-urea  (p.  282),  (JBaeyer);  (3)  by  the  saponification  of 
cyan-acetic  acid,  (Kolbe,  MuUer ;  A.  131,  348;  204,  121): 

CH2(CN)— CO2H  +  2H2O   =  GB^iCO^R)^  +  NH3. 

Large  plates  or  tables,  readily  soluble  in  water,  alcohol  and 
ether.  M.  Pt.  132°.  Decomposes  upon  heating,  as  given  at 
p.  230. 

Ethyl  malonate,  malonic  ether,  CB.^{CO.OG^ll^)^.  This 
ether,  which  is  directly  obtainable  from  cyan-acetic  acid  by 
leading  HCl  gas  into  its  solution  in  absolute  alcohol,  is  a  liquid 
of  faint  aromatic  odour  boiling  at  195°,  and  having  a  remark- 
able similarity  to  aceto- acetic  ether.  Thus  the  hydrogen  of 
the  methylene  group  is  here,  as  in  the  case  of  the  latter, 
replaceable  by  sodium,  through  the  influence  of  the  carbonyl 
groups,  CO,  which  are  also  bound  to  the  methylene ;  and  the 
resulting  sodio-malonic  ether  readily  exchanges  the  metal  for 


234 


X.   DIBASIC  ACIDS. 


alkyl  upon  treatment  with  alkyl  iodide.  By  this  means  the 
higher  homologues  of  malonic  ether,  e.g.  methyl-,  ethyl-, 
propyl-  etc.,  malonic  ethers,  are  obtained.  Further,  the  second 
hydrogen  atom  in  these  can  be  exchanged  in  exactly  the  same 
manner  for  sodium  and  then  for  alkyl,  whereby  di-alkyl 
malonic  acids  result.  This  is  an  important  method  for  the 
preparation  of  the  higher  dibasic  acids,  being  applicable  even  in 
complicated  cases ;  it  is  termed  the  malonic-ether  synthesis." 
(Of  Conrad  and  Bisclioff,  A.  204,  121.) 

By  the  splitting  off  of  COg  from  these,  the  higher  monobasic  acids . 
are  obtained,  (indirect  synthesis,  see  p.  150,  10''). 

Upon  heating  malonic  ether  with  its  sodium  compound,  a  derivative 
of  phloroglucin  results.    (See  this,  also  B.  18,  3454.) 

Chloro-malonic  ether,  CHC1(C02C2H5)2,  a  liquid  boiling  at  222°,  is 
employed  in  analogous  syntheses,  and  otherwise  reacts  in  a  similar  way 
to  chloracetic  ether. 

Succinic  acids.  (1)  Common  Succinic  acid,  ethylene-succinic 
acid^  symmetrical  ethane-dicarboxylic  acid,  acidum  succinicum  (from 
succinum,  amber),  COgH — — CHg — COgH.  This  acid  has 
been  known  for  a  long  time ;  its  composition  was  determined 
by  Berzelius. 

Occurrence.  In  amber,  in  various  resins  and  lignites,  in  many 
compositse,  in  Papavaraceae,  in  unripe  wine  grapes,  urine,  blood, 
etc. 

Formation,  (a)  From  ethylene  cyanide,  according  to  2,  p. 
228  ;  (b)  From  /^-iodo-  (and  cyano-)  propionic  acid,  according  to 
2* ;  (c)  By  the  reduction  of  fumaric  and  maleic  acids,  C^H^O^  ; 

(d)  By  heating  its  oxy-acids,  malic  or  tartaric,  with  hydriodic 
acid,  and  also  by  certain  fermentations  of  these,  e.g.  from  the 
former  according  to  the  equation  : 

CJI,{OR)0,  +  2HI  =  +  I2; 

(e)  As  a  bye-product  in  the  alcoholic  fermentation  of  sugar ; 
(/)  By  the  oxidation  of  fats,  fatty  acids  and  paraffins  by  means 
of  nitric  acid. 

Preparation.  From  calcium  malate  according  to  d,  by  fer- 
mentation, or  by  the  distillation  of  amber. 


SUCCINIC  ACIDS,  ETC. 


235 


Properties,  Monoclinic  prisms  or  tables  of  an  unpleasant 
faintly  acid  taste.  Rather  easily  soluble  in  water.  M.  Pt. 
185°,  B.  Pt.  285°.  Yields  succinic  anhydride — (long  needles) 
— upon  distillation.  For  its  electrolysis,  see  p.  49.  Is  very 
stable  towards  oxidizing  agents. 

Of  the  Salts  of  succinic  acid,  the  basic  ferric  salt,  obtained  by  the 
addition  of  a  ferric  salt  to  ammonium  succinate,  is  used  in  analysis  for 
the  separation  of  iron  from  alumina.  The  calcium  salt  is  soluble  in 
water. 

The  Derivatives  of  succinic  acid  correspond  exactly  with  those  of 
oxalic,  e.g.  Succinamic  acid,  C2H4(C02H)(CO.NH2),  is  analogous  to 
oxamic  acid  ;  in  this  case,  however,  the  normal  chloride,  Succinyl 
chloride,  C2H4(C0C1)2,  the  analogue  of  acetyl  chloride  in  all  its 
important  properties,  is  known.  In  addition  to  the  Amides,  there 
exists — as  in  the  case  of  other  dibasic  acids — an  imide,  Succinimide, 
CO 

C2H4<^QQ^NH.     The  latter  crystallizes  in  rhombic  plates,  and  is 

formed  by  heating  acid  succinate  of  ammonium.  The  basic  properties 
of  the  NHg  are  so  modified  by  the  two  carbonyl  groups  of  the  acid 
radicle  that  the  imido-hydrogen  is  replaceable  by  metals,  such  as  K, 
Ag,  etc. 

Mono-  and  Di-bromo-succinic  acids,  C2H3Br(C02H)2  and  C2H2Br2(C02H)2, 
are  easily  prepared  and  are  valuable  for  the  syntheses  of  the  oxy-suc- 
cinic  acids. 

By  the  action  of  sodium  upon  succinic  ethyl  ether  there  is  formed 
succino- succinic  ether,  C6H602(C02G2H5)2,  a  derivative  of  benzene. 
For  Acetol-  and  Di-acetol-succinic  ethers,  see  p.  227. 

(2)  Iso-succinicacid,e%?i6?67i6-5i^camca(5i6?,  CH3 — CH(C02H)2, 
is  formed  e.g.  by  the  malonic  ether  synthesis,  or  from  a-chloro- 
(or  iodo-)  propionic  acid,  (pp.  234  and  229).  Needles  or 
prisms.  Decomposes  upon  heating  into  COg  and  propionic 
acid,  and  yields  no  anhydride,  (p.  230). 

Pyrotartaric  acids,  C3Hg(C02H)2.  Of  these  four  are  known, 
this  being  the  number  theoretically  possible.  The  two  follow- 
ing may  be  mentioned  here  : 

1.  Glutaric  acid,  normal  pyrotartaric  acid,  COgH — CH2  — 
CHg — CH2 — COgH,  is  of  interest  on  account  of  its  relation  to 
piperidene. 

2.  Pyrotartaric  acid,  methyl-succinic  acid,  COgH— CH2 — 
CH(CH3) — COjH,  results,  among  other  methods,  along  with 


236 


X.   DIBASIC  ACIDS. 


pyroracemic  acid  hy  the  dry  distillation  of  tartaric  acid,  by 
the  ace  to-acetic  ether  synthesis,  etc.  Small  triclinic  prisms. 
M.  Pt.  1 1  2°.    Forms  an  anhydride. 

The  higher  homologues  (see  Summary,  p.  228)  are  formed  along 
with  succinic  and  oxalic  acids  by  the  oxidation  of  fats,  oils,  cork,  etc., 
by  means  of  nitric  acid. 


B.  Unsaturated  dibasic  Acids,  C^Hg^.A. 

Fumaric  acid,\p  tt        -rrx        Itaconic  acid,] 

Maleic      „  /^2^2l^^2^;2-      Citraconic  „  C3H4(C02H)2. 

Mesaconic  J 
Hydro-muconic  acid )  Q  jj  Q      Teraconic  C^H-^^^O^, 
Pyro-cinchonic    „    |  6  8  4-  q^q^ 

The  unsaturated  acids  stand  in  the  same  relation  to  the 
saturated  dibasic  acids  as  acrylic  acid  does  to  propionic.  As 
acids  they  yield  derivatives  analogous  to  those  of  the  acids 
CnH2n-204,  whilc  as  unsaturated  compounds  they  possess,  in 
addition,  the  faculty  of  combining  with  two  atoms  of  hydrogen 
or  halogen,  or  with  one  molecule  halogen  hydride. 

Formation.  1 .  By  the  elimination  of  water  from  the  dibasic 
oxy-acids.  Thus  malic  acid  yields  upon  distillation  water 
and  maleic  anhydride,  which  volatilizes,  and  also  fumaric  acid, 
which  remains  behind : 

Citric  acid  yields  in  a  similar  way  CO2,  H2O,  itaconic  acid 
and  citraconic  anhydride. 

2.  By  the  separation  of  halogen  hydride  from  the  mono-haloid 
substitution  products  of  succinic  acid  and  its  homologues,  monobromo- 
succinic  acid  yielding  fumaric,  thus  : 

C4H5Br04-HBr  =  C4H4O4. 

2\  From  the  analogous  di-substitution  products  by  the  separation 
of  the  halogen. 

The  cases  of  isomerism  among  the  acids  C^H2n_404  are  of 
great  interest  (see  next  page). 


FUMARIC  AND  MALEIC  ACIDS. 


237 


Constitution,  The  acids  of  this  series  may  be  regarded  as 
di-carboxylic  acids  of  the  olefines,  e.g.  fumaric  and  maleic  acids, 
C2H2(C02H)2,  as  those  of  ethylene.    Their  mode  of  formation 

1.  corresponds  exactly  with  the  production  of  ethylene  from 
alcohol,  or  with  that  of  acrylic  from  ethylene-lactic  acid,  while 

2.  agrees  with  that  of  ethylene  from  ethyl  iodide. 

Maleic  acid,  CgHglCOgHjg.  Large  prisms  of  a  grating  nauseous  acid 
taste,  very  readily  soluble  in  cold  water.  Distils  unchanged,  excepting 
for  partial  transformation  into  maleic  anhydride,  €2112(002)20.  Is 
conveniently  prepared  by  heating  the  acetyl  derivative  of  malic  acid, 
(see  p.  239,  also  B.  14,  2791). 

Fumaric  acid,  C2H2(C02H)2.  Small  prisms  of  a  strong,  purely  acid 
taste,  almost  insoluble  in  cold  water.  Sublimes  at  about  200°  with 
formation  of  maleic  anhydride.  Occurs  in  Fumaria  officinalis,  various 
fungi,  truffles,  Iceland  moss,  etc.,  and  is  obtained  from  maleic  acid 
either  by  prolonged  heating  of  the  latter  at  130°,  or  by  the  action  upon 
it  of  hydrobromic  or  other  acids. 

Both  acids  are  converted  into  their  ethers  on  treating  their  silver 
salts  with  alkyl  iodide,  these  ethers  also  standing  in  very  close  relation 
to  one  another ;  thus  ethylic  maleate  is  changed  into  ethylic  fumarate 
when  warmed  with  iodine,  and  the  latter  results  directly  from  the 
etherification  of  maleic  acid  in  alcoholic  solution  by  means  of  HCl. 

Both  acids  yield  common  succinic  acid  with  nascent  hydrogen, 
and  probably  contain  in  consequence  the  same  carbon  chain,  which 
would  lead  to  the  same  constitutional  formula  for  both,  viz., 
C02H-^CH-CH-C02H  (I.). 

The  explanation  of  the  isomerism  of  these  acids  has  thus  to  contend 
with  difficulties  which  it  has  been  attempted  to  remove  as  follows  : 
(a)  by  the  assumption  that  maleic  acid  has  the  formula  (I.),  but  fumaric 
— on  the  other  hand — the  constitution  CH2=C(C02H)2  (II.),  the  latter 
atomic  grouping  being  held  to  be  easily  convertible  into  the  isomeric 
form  (I.) ;  (6)  by  the  aid  of  conceptions  with  regard  to  the  arrangement 
of  atoms  in  space,  according  to  van  H  Hoff  (cf.  pp.  19  and  31),  concep- 
tions which  Wislicenus  has  extended  in  the  most  interesting  manner  at 
p.  180  of  the  memoir  already  cited  (p.  19) ;  (c)  by  the  assumption  of 
relations  between  fumaric  and  maleic  acids  similar  to  those  between 
racemic  and  inactive  tartaric  acids,  {KehuU  and  Anschutz,  B.  14,  717  ; 
18,  1400)  ;  (d)  by  the  assumption  of  free  affinities  in  maleic  acid, 
{Fittig), 

Similar  isomeric  relations  exist  between  the  homologous  acids, 
itaconic  and  citraconic.  (Cf.  KdcuJAy  A.  Suppl.,  I.  129  ;  II.,  Ill  ;  Fittig, 
A.  188,  95;  195,  56;  216,  77,  etc.) 


238 


X.   DIBASIC  ACIDS. 


Appendix.  Acetylene-dicarboxylic  acid,  CO^H— C=C— CO2H, 
Di  -  acetylene  dicarboxy  lie  acid,  COgH— C  =  C— C=C— COgH,  and  Tetr- 
acetylene-dicarboxylic  acid,  COgH— C=C— C=C— C=C— C=C— COgH, 
have  been  prepared  by  Ba^yer  (B.  15,  2695  ;  18,  678  and  22C9).  With 
increasing  length  of  chain  they  show  an  increasing  tendency  to  explode, 
(cf.  copper-acetylene.)  For  Baeyer's  theory  of  explosions  see  B.  18, 
2277. 


0.  Triatomic  dibasic  Acids,  C^Hsn-aOg. 

1.  Tartronic  acid,  oxy-malonic  acid^  C3H4O5,  =  CH(OH)(C02H)2. 
This  acid  forms  large  prisms  (+  ^HgO),  easily  soluble  in 
water,  alcohol  and  ether.  It  cannot  be  distilled  unchanged, 
since  it  breaks  up  on  heating  into  carbon  dioxide  and  glycolide. 

Formation.  1.  As  oxy-malonic  acid,  from  chloro-malonic  acid  by 
the  exchange  of  CI  for  OH. 

2.  As  a  derivative  of  the  triatomic  glycerine,  by  oxidizing  the  latter 
with  permanganate  of  potash. 

3.  By  reduction  of  the  corresponding  ketonic  acid,  mesoxalic  acid, 
CO{C02H)2,  just  as  lactic  acid  is  obtained  from  pyroracemic  acid. 

Preparation.  By  the  spontaneous  decomposition  of  the  so-called 
nitro-tartaric  acid  (p.  241,  Dessaignes),  dioxy-tartaric  acid  being 
formed  as  intermediate  product  (KehuU) ;  also  from  chloral  hydro- 
cyanate,  (B.  18,  2852). 

2.  Malic  acid,  oxy-succinic  acid,  acidum  malicum^  C^HgOg, 
=  C2H3(OH)(C02H)2,  =  CO2H— CH2— CH(OH)— CO2H, 
{ScheeU,  1785). 

Occurrence,  Is  very  widely  distributed  in  the  vegetable 
kingdom,  being  found  in  unripe  apples,  sorb-apples,  grapes, 
barberries,  quinces,  Crassulacese,  etc. 

Formation.  1.  As  oxy-succinic  acid,  by  treating  bromo- 
succinic  acid  with  moist  oxide  of  silver  : 

C2H3Br(C02H)2  +  HgO  =  C2H3(OH)(C02H)2  +  HBr. 

2.  By  the  reduction  of  tartaric  or  racemic  acid  with  HI. 

3.  From  aspartic  acid  or  asparagine  by  means  of  N2O3. 

4.  By  heating  fumaric  or  maleic  acid  with  water,  (A.  192, 
80). 


MALIC  ACID. 


239 


Properties.  Hygroscopic  glancing  needles,  usually  in  round 
groups,  readily  soluble  in  water  and  alcohol,  but  only  slightly 
in  ether.  M.  Pt.  100°.  When  it  is  distilled,  maleic  anhydride 
passes  over  and  fumaric  acid  remains  in  the  retort. 

Yields,  when  heated  with  concentrated  H2SO4,  Cumalic  acid, 
CgHgOslCOgH).    (B.  17,  936.) 

Malic  acid  exists  in  several  optically  dilfferent  modifications  which 
correspond  exactly  with  those  of  tartaric  acid.  The  dilute  solution  of 
the  natural  acid  is  Isevo- rotatory  ;  the  acid  obtained  from  dextro- tartaric 
acid  is  dextro-rotatory  ;  while  the, acid  prepared  from  racemic,  succinic, 
or  fumaric  acid  is  inactive,  and  can  be  separated  into  the  active  modifi- 
cations. 

The  alkaline  salts  and  the  acid  calcium  salt  of  malic  acid  are  readily 
soluble  in  water,  while  the  neutral  calcium  salt  is  only  sparingly 
soluble.  As  an  alcohol,  the  acid  yields  ethers,  e.^.,  an  Acetyl-malic 
acid,  C2H3(O.C2H30)(C02H)2. 

Amides  and  Amines  of  malic  acid.  Like  glycoUic  acid, 
malic  acid  forms — as  an  acid — amides  (saponifiable),  and — as 
an  alcohol — an  amine  (not  saponifiable).    The  amides  are  : 

Malamide,  C2H3(OH)(CO.NH2)2,  crystallizing  in  prisms, 
and  Malamic  acid,  C2H3(OH)(CO.NH2)(C02H),  the  latter  being 
known  as  ethyl  ether.  The  alcoholic  amine,  aspartic  acid, 
C2H3(NB[2)(C02H)2,  unites  in  itself  like  glycocoll  the  properties 
of  a  base  and  of  an  acid,  but  the  acid  character  predominates. 
Its  acid  amide  is  asparagine.  The  neutral  amide  has  also  been 
prepared  synthetically  from  bromo-succinic  ethyl  ether  and 
ammonia ;  it  is  readily  transformed  into  asparagine,  (B.  20, 
E.  511). 

\^  Asparagine,  C2H3(NH2)(CO.NH2)(C02H),  which  is  isomeric 
with  malamide,  is  very  widely  distributed  in  the  vegetable 
kingdom,  being  present  in  the  young  leaves  of  trees,  in  beet- 
root, potatoes,  the  shoots  of  peas,  beans  and  vetches,  and  in 
asparagus ;  it  was  first  found  in  the  last-named  vegetable  in 
the  year  1805.  It  forms  glancing  rhombic  prisms  (-1-H2O), 
easily  soluble  in  hot  water,  but  insoluble  in  alcohol  and  ether. 
Goes  into  aspartic  acid  on  saponification.    Is  optically  active. 

Aspartic  acid,  C2H3(NH2)(C02H)2,  is  present  in  beet 
molasses  and  forms  an  important  product  of  the  decomposition 


240 


X.  DIBASIC  ACIDS. 


of  albuminoid  substances  by  means  of  acids  or  alkalies.  Small 
rhombic  tables,  rather  easily  soluble  in  hot  water.  It  exists 
in  several  optically  dilferent  modifications,  which  differ  in 
taste  and  are  convertible,  the  one  into  the  other,  (B.  20, 
E.  510).  Nitrous  acid  transforms  it,  as  well  as  asparagine, 
into  malic  acid,  (normal  amine  and  amide  reaction). 

Just  as  glycocoU  is  to  be  regarded  as  amido-acetic  acid,  so 
is  aspartic  acid  to  be  looked  upon  as  amido-succinic. 

Isomers  of  malic  acid  are  both  possible  and  known. 


Higher  Homologues, 
a-Oxy-glutaric  "v  Diaterebic  acid,  C5H9(OH)(C02H)2. 

Itamalic  acid,  psHstOHllCOaHja.  Di^^-^^pg^yii^,  CgHnlOHXCOaHja. 
Citramalic  acid,  ^  etc. 

Glutamlne,  C3H5(NH2)(CO.NH2)(C02H),  and  Glutamic  acid, 
C3Hg(NH2)(C02H)2,  are  the  ammonia  derivatives  of  a-oxy-glutaric 
acid,  being  homologous  with  asparagine  and  aspartic  acid.  The 
former  is  likewise  found  in  beetroot  and  in  the  shoots  of  the  vetch 
and  gourd,  while  the  latter  is  produced,  together  with  aspartic  acid  and 
leucine,  by  boiling  albuminous  compounds  with  dilute  sulphuric  acid. 


D.  Tetratomic  dibasic  Acids. 

Tetratomic  dibasic  acids  are  such  as  unite  in  themselves 
the  properties  of  a  diatomic  alcohol  with  those  of  a  dibasic 
acid.  Theoretically  they  are  characterized  by  the  presence  of 
two  alcoholic  hydroxyls  and  two  carboxyls  in  the  molecule. 

The  simplest  possible  member  of  the  series,  the  compound 
C(OH)2(C02H)2,  is  unstable  and  has  not  the  characters  of  an  alcoholic 
acid,  but  those  of  the  hydrate  of  a  ketonic  acid,  since  it  contains  two 
hydroxyls  bound  to  the  same  carbon  atom.  (See  Mesoxalic  acid, 
p.  244.) 

Tartaric  acid,  dioxy-succinic  acid,  oxy-malic  acid,  G^^Oq, 
=  C2H,(OH)2(C02H),,  =  C02H-CH(OH)-CH(OH)-(C02H). 
This  acid  exists  in  four  "  physically  isomeric  "  modifications. 

1.  Dextro-tartaric  acid,  acidum  tartaricuin,  is  the  tartaric 


TARTARIC  ACIDS. 


241 


acid  found  in  nature.  It  was  discovered  by  Scheele  in  1769. 
It  occurs  in  the  free  state  or  as  salt,  chiefly  acid  potassium 
salt,  in  various  fruits,  especially  in  the  juice  of  grapes,  from 
which  bitartrate  of  potash  or  tartar — (tartarus) — separates  in 
crystals  during  fermentation.  When  this  is  boiled  with  chalk 
and  chloride  of  calcium  it  is  transformed  into  the  neutral  lime 
salt,  from  which  the  acid  is  liberated  on  addition  of  HgSO^. 

Large  transparent  monoclinic  prisms,  of  a  strong  and  purely 
acid  taste,  very  easily  soluble  in  water,  readily  also  in  alcohol, 
but  almost  insoluble  in  ether.  M.  Pt.  135°.  Reduces  an 
ammoniacal  silver  solution  upon  warming.  When  melted,  it 
is  changed  into  an  amorphous  modification  and  then  into  an 
anhydride,  and  when  heated  more  strongly  it  carbonizes,  with 
the  dissemination  of  a  characteristic  odour  and  formation  of 
pyroracemic  and  pyrotartaric  acids.  Oxidation  converts  it 
either  into  dioxy-tartaric  or  tartronic  acid,  and  then  into 
formic  and  carbonic  acids,  etc. 

Neutral  potassium  tartrate,  C4H4O6K2  +  JHgO,  forms  monoclinic 
prisms  easily  soluble  in  water. 

Acid  potassium  tartrate,  Tartar,  or  Cremor  tartari,  C4H5O6K.  Small 
rhombic  crystals  of  acid  taste,  sparingly  soluble  in  water ;  is  much  used 
in  dyeing,  medicine,  etc. 

Potassium-sodium  tartrate,  Rochelle  or  Seignette  salt,  C4H406KIsra 
4-  4H2O  (1672),  forms  magnificent  rhombic  prisms. 

Calcium  tartrate,  C4H406Ca  +  4H2O,  is  a  powder  insoluble  in  water 
but  soluble  in  cold  caustic  soda  solution  ;  on  warming  the  solution  it 
separates  as  a  jelly,  which  redissolves  upon  cooling. 

Potassio-antimonious  tartrate,  Tartar  emetic,  C4H4(SbO)'KOg  + JH2O, 
(see  B.  15,  1540),  is  obtained  by  heating  cream  of  tartar  with  antimony 
oxide  and  water.  Rhombic  efflorescent  octahedra,  easily  soluble  in 
water.  It  is  poisonous  and  acts  as  an  emetic,  and  is  used  as  a  mordant 
in  dyeing. 

Feldimfs  solution  is  a  solution  of  cupric  sulphate  mixed  with  alkali 
and  seignette  salt. 

The  Di  ethyl  ether  is  a  thick  oil,  while  the  Mono-ethyl  ether 
crystallizes  in  prisms.  Acetyl -tartaric  acid  and  Amides  of  tartaric  acid 
are  known,  and  also  various  anhydrides.  As  an  alcohol,  it  forms 
with  nitric  acid  a  di-nitric  ether,  the  so-called  Nitre -tartaric  acid, 
C2H2(O.N02)2(CO.^H).j,  which  as  an  ether  is  readily  saponifiable  and, 
generally  speaking,  easily  decomposable  with  formation  of  Dioxy- 
tartaric  or  of  tartronic  acid. 

(  50(5 )  Q 


242 


X.  DIBASIC  ACIDS. 


Aqueous  solutions  of  ordinary  tartaric  acid  or  of  its  salts 
turn  the  plane  of  polarization  of  light  to  the  right ;  the  nature 
of  the  solvent  affects  this  action,  (B.  18,  Ref.  591).  The  acid 
is  employed  in  medicine,  dyeing,  etc. 

2.  Laevo-tartaric  acid  is  identical  in  its  chemical  and  also 
in  almost  all  its  physical  properties  with  ordinary  tartaric  acid, 
but  differs  from  it  in  that  it  turns  the  plane  of  polarization  of 
light  to  the  left,  in  a  degree  equal  to  that  in  which  the  other 
turns  it  to  the  right.  The  crystallized  salts  show  hemihedral 
faces  like  the  salts  of  dextro-tartaric  acid,  but  oppositely 
situated  (see  below).  When  equal  quantities  of  both  acids 
are  mixed  together  in  aqueous  solution,  the  solution  becomes 
warm,  and  we  obtain 

3.  Racemic  acid,  GJIqOq  +  HgO,  the  composition  of  which 
was  first  established  by  Berzelius,  who  recognized  it  as  being 
different  from  tartaric  acid,  and  who  developed  the  idea  of 
isomerism  from  this  first  example  in  1829.  Racemic  acid  is 
obtained  from  tartar  mother  liquor.  It  differs  from  dextro- 
tartaric  acid  in  that  its  crystals  are  rhombic  and  efflorescent 
and  also  less  soluble  in  water  than  the  former;  further,  the 
free  acid  is  capable  of  precipitating  a  solution  of  calcium 
chloride  and  is  optically  inactive  (see  below).  The  salts, 
which  are  termed  racemates,  and  also  the  ethers  (B.  21,  518), 
show  small  differences  from  the  tartrates  in  the  proportions  of 
their  water  of  crystallization  and  in  solubility. 

When  a  solution  of  sodium-ammonium racemate,  C4H4Na(NH4)Og  +  4H2O, 
is  evaporated,  beautiful  rhombic  crystals  which  show  hemihedral  faces 
are  obtained.  Pasteur  observed  that  these  faces  were  not  always 
similarly  situated,  but  that  certain  crystals  were  dextro-hemihedral 
while  others  were  Isevo-hemihedral,  so  that  one  crystal  formed  the 
reflected  image  of  the  other.  The  Isevo -hemihedral  crystals  are  opti- 
cally dextro-rotatory  and  vice  versa.  If  now  the  two  kinds  of  crystals 
be  separated  from  one  another  mechanically  and  the  free  acid  liberated 
from  each,  this  will  be  found  to  consist,  not  of  racemic  acid,  but  in  the 
one  case  of  dextro-  and  in  the  other  of  Isevo-tartaric  acid. 

An  analogous  decomposition  of  racemic  acid  is  also  possible  by 
other  means,  (cf.  p.  31). 

4.  Me£0-tartaric  acid,  a  fourth  tartaric  acid,  is  inactive  like 


FORMATION  OF  THE  TARTARIC  ACIDS,  ETC. 


243 


the  foregoing  but  not  decomposable  into  the  active  acids, 
although  it  can  be  transformed  into  the  latter  (see  below).  It 
crystallizes  in  efflorescent  rectangular  plates.  The  acid  potas- 
sium salt  is  easily  soluble  in  water. 


1.  The  oxidation  of  mannite  by  means  of  HNO3  yields  racemic  acid, 
and  that  of  sorbin,  meso- tartaric  acid. 

2.  The  treatment  of  dibromo-succinic  acid,  C2H2Br2(C02H)2, 
with  moist  oxide  of  silver  yields  racemic  and  meso-tartaric 
acids  (KekuU), 

3.  Racemic  acid  results  from  the  saponification  of  the  cyanhydrin  of 
glyoxal,  (cf.  p.  133). 

4.  The  oxidation  of  fumaric  acid  by  means  of  KMn04  yields  racemic 
acid,  and  that  of  maleic,  meso-tartaric  acid  (KeJcuU), 

5.  When  dextro-  or  Isevo-tartaric  acid  is  heated  with  some  water  to 
170°,  racemic  and  meso-tartaric  acids  are  formed  ;  meso-tartaric  acid 
changes  partially  into  racemic  acid  under  analogous  conditions,  a  state 
of  equilibrium  being  reached  here. 

For  the  splitting  up  of  racemic  acid,  see  above. 

The  isomeric  relations  of  the  tartaric  acids  are  easily  explic- 
able by  the  aid  of  conceptions  as  to  the  modes  in  which  the 
atoms  and  atomic  groups  are  linked  in  space  to  asymmetric 
carbon  atoms,  which  are  present  not  only  in  them  but  also  in 
malic  acid,  asparagine,  lactic  acid,  active  amyl  alcohol,  etc., 
(see  pp.  19,  31,  and  32). 

E.  Penta-  and  Hexatomic  dibasic  Acids. 

Pentatomic  :  Aposorbic  acid,  C3H3(OH)3(C02H)2. 
Hexatomic  :    Dioxy-tartaric   acid,   C2(OH)4(C02H)2,  (see 
Ketonic  acids). 

Saccharic  acid,^ 


Formation  of  the  Tartaric  Acids, 


Mucic 

Iso-saccharic 
Glycuronic 


244 


X.  DIBASIC  ACIDS. 


Saccharic  acid  is  produced  by  the  oxidation  of  cane  sugar,  glucose, 
mannite  or  starch  by  HNO3,  and  Mucic  acid  by  that  of  gums,  mucilages 
and  milk  sugar.  The  former  is  hygroscopic  and  easily  soluble  in  water, 
the  latter  a  difficultly  soluble  white  crystalline  powder.  Isosaccharic 
acid  is  obtained  by  the  oxidation  of  glucosamine,  C6H]_i05(NH2).  These 
acids  form,  as  tetratomic  alcohols,  tetra-acetyl  derivatives,  etc.,  and,  as 
acids,  two  series  of  salts,  ethers,  etc.  Their  constitution  still  requires 
further  investigation.  Mucic  acid  readily  changes  into  f urfurane  deriva- 
tives (see  p.  298).  Glycuronic  acid  is  a  decomposition  product  of  a  series 
of  complicated  compounds  which  are  found  in  the  urine  after  the  con- 
sumption of  camphor,  phenol,  etc.,  (**  phenyl-glycuronic  acid").  It 
forms  a  syrupy  mass. 

F.  Dibasic  Ketonic  Acids. 

Dibasic  ketonic  acids  unite  in  themselves  the  properties  of  a 
ketone  and  of  a  dibasic  acid.    The  following  are  known  : 

1.  Mesoxalic  acid,  CO(C02H)2  or  C(OH)2(C02H)2  (see  p. 
240),  is  prepared  from  dibromo-malonic  acid,  CBr2(C02H)2,  and 
baryta  water  or  oxide  of  silver,  thus  : 

CBr2(C02H)2  +  H2O  =  CO(C02H)2  +  2HBr; 

also  by  boiling  alloxan  (p.  282)  with  baryta  water.  It 
crystallizes  in  deliquescent  prisms  (  +  H2O). 

As  a  ketone  it  combines  with  NaHSOg,  reacts  with  hydroxyl- 
amine  (p.  142),  and  is  reduced  by  nascent  hydrogen  to  the 
corresponding  secondary  alcohol-acid,  tartronic  acid : 

CO(C02H)2  +  H2  =  CH(OH)(C02H)2. 

Since  the  acid  and  its  salts  still  retain  a  molecule  of  water  at  tempera- 
tures above  100°,  this  may  be  chemically  bound  as  in  chloral  hydrate, 
corresponding  to  the  formula,  C(OH)2(C02H)2,  di-oxy-malonic  acid." 
In  agreement  with  this,  a  di-acetyl  compound,  C(0. 031130)2(00202115)2, 
can  be  prepared. 

2.  Acetone-dicarboxyHc  acid,  OgHgOg,  =  C0=(CH2 — 002H)2,  results 
upon  treating  citric  acid  with  concentrated  H2SO4.  It  breaks  up  readily 
into  acetone  and  2CO2,  (see  B.  17,  2542). 

Dioxy-tartaric  acid,  OOgH— 00 — 00 — COgH,  or  probably 
CO2H— C(0H)2— C(0H)2— OO2H,  is  formed  from  pyro-catechin  and 
nitrous  acid,  and  by  the  gradual  decomposition  of  nitro- tartaric  acid. 
It  does  not  exist  in  the  free  state.    The  characteristic  difficultly  soluble 


TRI-  TO  HEXATOMIG  ACIDS. 


245 


sodium  salt  decomposes  easily  into  CO2  and  tartronate  of  sodium.  It 
reacts  with  two  mols.  hydroxylamine.  With  phenyl-hydrazine-sulph- 
onic  acid,  a  dye  "tartrazine"  is  produced,  (cf.  KeJcuUy  A.  221,  230.) 


XL  TRI-  TO  HEXABASIO  ACIDS. 

The  tribasic  organic  acids  are  those  which,  like  phosphoric 
acid,  are  capable  of  forming  three  series  of  salts,  viz.,  neutral, 
mono-acid  and  di-acid  salts.  They  contain  according  to 
theory  three  carboxyl  groups.  There  are  not  only  triatomic 
tribasic  acids,  such  as  methane-  and  propane-tri-carboxylic 
acids,  etc.,  which  are  of  purely  acid  character,  but  also 
tetratomic,  pentatomic  and  hexatomic  tribasic  acids,  alcoholic 
acids  which  possess  at  the  same  time  the  characters  of  alcohols. 
Further,  these  may  be  derived  either  from  saturated  or  from 
unsaturated  hydrocarbons. 

A.  Triatomic  tribasic  Acids. 

1.  Methane-tricarboxylic  acid,  CH(C02H)3, 

2.  Ethane-tricarboxylic      „  03113(00211)3, 

3.  Propane-tricarboxylic    „  03H5(002H)3, 

4.  Tricarballylic  „  03H5(002H)3. 

The  above  acids  1  to  3  have  been  prepared  by  the  malonic  ether 
synthesis  ;  they  are  for  the  most  part  known  as  ethers,  some  of  them 
being  incapable  of  existence  in  the  free  state,  while  others  readily  break 
up  upon  heating  into  CO2  and  dibasic  acids. 

Propane-tricarboxylic  acid  is  unsymmetrically  constituted. 

Tricarballylic  acid,  symmetrical  propane-tricarhoxylic  acid, 
03X15(00211)3.  Occurs  in  unripe  beet,  and  is  prepared 
synthetically  from  glycerine  by  transforming  it  into  tri-brom- 
hydrin,  03H5Br3,  treating  this  with  KON,  and  saponifying  the 
cyanide  formed,  03H5(ON)3.  Since  the  three  hydroxyls  in 
glycerine  are  distributed  among  three  carbon  atoms,  the  same 
holds  good  for  the  carboxyls  in  the  acid,  which  has  therefore 
the  symmetrical  constitution : 


246 


XI.  TRI-  TO  HEXATOMIC  ACIDS. 


CH2— CO2H 

CH— CO2H 

CH2— CO2H. 

This  acid  is  of  importance  in  determining  the  constitution 
of  citric  acid,  from  which  it  can  be  obtained  by  heating  with 
HI.  It  also  results  from  the  addition  of  Hg  to  aconitic  acid, 
CgHgOg.  It  crystallizes  in  rhombic  prisms,  easily  soluble  in 
water,  etc.    M.  Pt.  166^ 

B.  An  Unsaturated  tribasic  Acid 

is  Aconitic  acid,  CgHgOg,  =  03113(00211)3,  which  contains 
two  atoms  of  hydrogen  less  than  tricarballylic  acid.  It  is 
found  in  nature,  in  Aconitum  Napellus,  shavegrass,  sugar  cane, 
beetroot,  etc.,  etc.,  and  is  prepared  by  heating  citric  acid, 
CgHgO^,  water  separating.  It  is  a  strong  acid,  crystallizable, 
and  easily  soluble  in  water.  M.  Pt.  186°.  Nascent  hydrogen 
transforms  it  into  tricarballylic  acid,  hence  it  is  an  unsaturated 
acid  and  its  constitution  is  : 

CH— OO2H 
C^002H 
CH2— CO2H. 

0.  Tetratomic  tribasic  Acids. 

Citric  acid,  acidum  citricum^  G^^O^,  =  03H4(0II)(002H)3. 
(Scheele,  1784;  recognized  as  tribasic  by  Liehig'm  1838.)  Occurs 
in  the  free  state  in  lemons,  oranges  and  red  bilberries,  and 
mixed  with  malic  acid  in  gooseberries,  etc.,  also  as  calcium 
salt  in  wood,  potatoes,  beetroot,  etc. 

Preparation.  From  the  juice  of  lemons  by  means  of  the 
lime  salt. 

Properties,  Large  rhombic  prisms  (+  H2O),  very  easily 
soluble  in  water  and  rather  easily  in  alcohol,  but  only  slightly 
in  ether.    It  loses  its  water  of  crystallization  at  135°,  melts 


CITRIC  ACID.  247 

at  l!)^,  and  breaks  up  at  a  higher  temperature  first  into  aconitic 
acid  and  water,  and  then  into  carbon  dioxide  and  itaconic 
acid  (and  also  acetone,  etc.).  Oxidizing  agents  effect  a  very 
thorough  decomposition. 

Citrate  of  calcium  is  precipitated  as  a  white  sandy  powder  upon 
boiling  a  mixture  of  calcium  chloride  and  alkaline  citrate.  The  three 
series  of  salts  are  well  characterized ;  the  alkaline  salts  are  soluble  in 
water,  the  others  mostly  insoluble.  Among  the  derivatives  may  be 
mentioned  mono-,  di-,  and  tri-ethyl  citrates  and  tri-ethyl  aceto-citrate, 
€3114(0. C2H30)(C02C2H5)3,  which,  last  forms  a  proof  of  the  alcoholic 
character  of  citric  acid  ;  it  boils  without  decomposition.  The  Amides  of 
citric  acid  are  converted  by  concentrated  H2SO4  into  Citrazinic  acid, 
C6H5NO4,  a  pyridine  derivative,  (B.  17,  2681.) 

The  constitution  of  citric  acid  is  arrived  at  both  from  its 
relation  to  aconitic  acid,  which  results  from  it  as  ethylene  does 
from  alcohol,  and  from  various  syntheses  ;  it  is  : 

CH2— CO2H 
C(OH)— CO2H 
CH2— CO2H. 

Thus  it  is  obtained  from  /3-dichloro-acetone  as  follows : 

CH,.CO,H 

C(0H)-C02H' 


H2CI 
0 
H2CI 


CH2CI 
C(OH)-CN 
CH2CI 


CH2CI 


CH2CI 


CH2.CN 
C(0H)-C02H 
CH2.CN 


C(0H).C02H 
CH2.CO2H. 


An  Iso-citric  acid,  isomeric  with  citric,  has  also  been  pre- 
pared  synthetically,  {Fittig,  B.  20,  3179). 

Appendix.  D.  Pentatomic  tribasic  acids.  Desoxanc  acid, 
CgHeOg,  =  C2H(OH)2(C02H)3,  and  Oxy-citric  acid,  CgHgOg,  the  latter 
of  which  is  present  in  the  juice  of  turnips. 

E.  Tetra-,  penta-,  and  hexabasic  acids  do  not  occur  in 
nature  but  have  been  prepared  in  considerable  numbers  by  means  of  the 
aceto-acetic  or  malonic  ether  synthesis,  e.gr.,  ethane-tetra-carboxylic 
acid,  propane-penta-carboxylic  acid  and  butane-hexa-carboxylic  acid. 
They  are  obtained  in  the  form  of  ethers,  most  of  them  being  either 
very  unstable  or  incapal)!:;  of  existence  in  the  free  state.  For  their 
preparation,  see  B.  15,  1109;  17,  2781  ;  A.  214,  31. 


248 


XII.  CYANOGEN  COMPOUNDS. 


XII.  CYANOGEN  COMPOUNDS. 

Under  the  name  of  the  cyanogen  compounds  is  included 
a  group  of  bodies  which  are  derivable  from  cyanogen,  CgNg. 
Cyanogen  itself  is  a  gas  of  excessively  poisonous  properties 
which  behaves  in  many  respects  like  a  halogen,  and  its 
hydrogen  compound,  hydrocyanic  acid,  HON,  is  an  acid  which 
is  very  similar  in  many  ways  to  hydrochloric.  In  many 
cyanogen  compounds  the  monovalent  group  (CN)  plays  the 
part  of  an  element ;  cyanogen  is  to  be  regarded  as  the  isolated 
radicle  (CN),  often  written  Cy,  which  however  possesses 
the  double  formula  C2N2,  just  as  a  molecule  of  chlorine  (Clg) 
is  made  up  of  two  atoms.  The  cyanogen  group  is  further 
capable  of  combining  with  the  halogens,  hydroxyl,  sulphydril 
(SH),  amidogen,  etc.,  etc.  From  the  compounds  so  obtained 
numerous  others  are  derived  by  the  entrance  of  alcohol 
radicles  in  place  of  hydrogen.  Such  derivatives  nearly  always 
exist  in  two  isomeric  forms,  sharply  distinguished  from  one 
another  by  their  properties,  and  whose  isomerism  is  of  very 
great  interest.    (See  table,  pp.  250  and  251.) 

There  exist  further  polymeric  modifications  of  most  of  those 
compounds  (see  table).  The  number  of  cyanogen  compounds 
known  is  thus  a  very  large  one. 

Formation.  1.  Carbon  and  nitrogen  cannot  combine  directly 
with  one  another  but  only  when  they  are  heated  in  presence 
of  an  alkali ;  thus,  when  nitrogen  is  led  over  a  red-hot  mixture 
of  coal  and  carbonate  of  potash,  potassium  cyanide,  KCN,  is 
formed. 

2.  By  passing  ammonia  over  red-hot  coal,  ammonium  cyanide, 
NH4CN,  is  produced. 

3.  Carbon  and  nitrogen  combine  most  readily  with  metals 
when  in  the  nascent  state,  e.g,^  when  nitrogenous  organic 
compounds  such  as  leather,  horn,  claws,  wool,  blood,  etc.,  are 
heated  with  potashes. 

4.  Hydrocyanic  acid  is  formed  when  electric  sparks  are  passed 
through  a  mixture  of  acetylene  and  nitrogen,  and  also  by  the  action 


CYANOGEN  ;  FORMATION  AND  PROPERTIES. 


249 


of  the  silent  electric  discharge  on  a  mixture  of  cyanogen  and  hydrogen. 
For  further  modes  of  formation,  see  below. 

The  original  material  for  the  preparation  of  most  of  the 
cyanogen  compounds  is  potassic  ferrocyanide,  which  is  manu- 
factured on  the  large  scale  and  possesses  the  great  advantages 
over  potassium  cyanide  of  being  stable  in  the  air  and  non- 
poisonous. 


A.  Cyanogen  and  Hydrocyanic  Acid. 

Cyanogen,  CgNg.    Discovered  by  Gay-Lussac  in  1815. 
Occurs  in  the  gases  of  blast-furnaces. 

Formation.  1.  As  the  nitrile  of  oxalic  acid,  by  the  abstraction 
of  the  elements  of  water  from  oxalate  of  ammonia  by  means  of 
PgOg ;  also  in  the  same  way  from  the  intermediate  product  of 
this  reaction,  oxamide : 

CA(NH4)2  -  4H2O  =  C2N2; 
C20,(NH,),  -  2H,0  =  C,N,. 

2.  By  heating  silver  cyanide,  AgCN,  or  mercuric  cyanide, 
Hg(CN)2,  strongly ;  this  is  the  method  followed  for  its  pre- 
paration : 

Hg(CN)2  =  Hg  +  C,N,. 

Further,  in  the  wet  way,  by  heating  a  solution  of  cupric 
sulphate  with  potassium  cyanide,  (B.  18,  Eef.  321). 

Cyanogen  is  a  colourless  gas  of  a  peculiar  unpleasant  odour 
resembling  that  of  bitter  almonds,  and  is  terribly  poisonous. 
Sp.  Gr.  1-8.  Easily  condensible.  M.  Pt.  -34°.  B.  Pt.  of 
liquid  cyanogen  -  21°.  Soluble  in  \  vol.  of  water  and  in  even 
less  alcohol.  The  solutions  become  dark  upon  standing,  with 
separation  of  a  brown  powder  ("  Azulmic  acid  while  oxalic 
acid,  ammonia,  formic  acid,  hydrocyanic  acid  and  urea  are  to 
be  found  in  the  liquid. 

The  formation  of  the  oxalic  acid  and  ammonia  dejjends  upon  normal 
saponification,  and  that  of  formic  acid  upon  the  saponification  of  the 

[Gontinwid  on  p.  252. 


250  XII.  CYANOGEN  COMPOUNDS. 

SUMMARY  OF  THE  CYANOGEN  COMPOUNDS  AND  OF 


Relation  to  carbonic 

Original  Compounds. 

acid,  etc. 
(See  p.  269.) 

Normal  Isomeric 
Form. 

Nitrile  of  oxalic  acid, 

Cyanogen, 

C2N2 

Nitrile  of  formic  acid, 

Hydrocyanic  acid, 
Alcoholic  derivatives  : 

(a)  Nitriles, 

{b)  Iso-nitriles, 

N=C.H 
CH3— C=N 

CH3— NC 

Cyanogen  chloride,  bro- 
mide, iodide, 

N=C.C1 

CO3H2  +  NH3-2H2O, 

(Partial  Nitrile,  event- 
ually Carbimide, 
see  p.  269), 

Cyanic  acid, 
Alcoholic  derivatives  : 

(a)  Methyl  cyanate, 
(6)      ,,  iso-cyanate. 

N=C— OH 
N=C-O.CHo 

0=C=N.CH3 

Alcoholic  derivatives  : 
(a)  Ethyl  thiocyanate. 

All,,!  J-Ui^ 

\o)  Ailyl  iso-tnio- 
cyanate, 

N=C— SH 
N^C-S.CgHs 

— 

S=C=NC3H5 

DO  H  +  2NH„  -  .^H^O 

(Nitrile  and  amide, 
eventually  Carbo-di- 
imide,  see  p.  269), 

Cyanamide, 
Alkylated  : 

{a)  Alkyl  cyanamide, 
(b)  Carbo-di-imide, 

N=C— NH2 
N=C— NH.CH3 

RN=C=NR* 

CO3H2  +  NH3-H2O, 
(Aminic  acid). 

Carbamic  acid, 

C0(NH2)0H 

/^r\  TT     1  OATTT        OUT  r\ 

(JU3XI2  +      rig  -  Zti20f 
(Carbamide), 

Urea, 

CO(NH2)2 

Thio-urea, 
Alkylated : 

(a)  Alkyl-thio-ureas, 

(b)  Imido-thio-carba- 
mine  compounds. 

CS(NH2)2 
CSN2H3R 

C(NH)^^^ 

CO3H2  +  3NH3-3H2O, 
(Amidines), 

Guanidine, 

C(NH)(NH2)2 

*  R  =  Alcohol  radicle. 


SUMMARY. 

SEVERAL  RELATED  CARBONIC  ACID  DERIVATIVES. 


251 


Polymeric  Compounds. 


Normal  Isomeric 
Form. 

Paracyanogen, 

(CN)x 

*'  Tri-hydrocyaiiic  acid,^^ 
Alcoholic  derivatives  : 
Cyanethine, 

(CNH)k 
(CN)3(C2H5)3 

— 

Cyanuric  chloride^  etc.^ 

(CN)3Cl3 

Cyanuric  acid, 
Alcoholic  derivatives  : 

(CN)3.(OH)3 

— 

(a)  Cyanurates, 

(b)  Iso-cyanurates, 

(CN)3.(OC2H5)3 

(CO)3.(NC2H5)3 

Dithio-dicyanic  acid," 
Thio-cyanuric  acid, 
Alcoholic  derivatives  : 
(a)  Thio- cyanurates, 

(CNSH)x 
(CN)3.(SH)3 

(CN)3.(SC2H5)3 

Dicyan-diamide, 
Melamine, 
Alkylated  : 

(a)  Alkyl-melamine, 

(b)  Alkyl-iso-melamine, 

C2N4H4 
(CN)3.(NH2)3 

(CN)3.(NHC2H5)3 

(C:NH)3(NC2H5)3 

No  Polymers. 

252 


XII.  CYANOGEN  COMPOUNDS. 


hydrocyanic  acid  formed  as  an  intermediate  product.  In  presence  of  a 
minute  quantity  of  aldehyde,  oxamide  results  from  the  taking  up  of 
water.  Cyanogen  combines  with  heated  potassium  to  KCN,  and  dis- 
solves in  aqueous  potash  to  form  KCN  and  KCNO.  It  yields  with  HgS 
the  thiamides  Flavean  hydride,  NC — CS.NH2,  and  Rubean  hydride, 
CS(NH2)-CS(NH2). 

Paracyanogen  (CN)x  is  a  polymer  of  cyanogen.  It  is  an  amorphous 
brown  powder  which  results  as  a  bye-product  when  mercuric  cyanide 
is  heated  ;  upon  further  heating,  it  is  transformed  into  cyanogen. 

Hydrocyanic  acid,  prussic  acid,  CNH.  Discovered  about 
the  year  1782  by  Scheele,  and  investigated  closely  by  Gay- 
Lussac. 

Formation.  1.  By  decomposing  metallic  cyanides  by  means 
of  stronger  acids  ;  also  by  the  distillation  of  potassic  ferro- 
cyanide  with  dilute  sulphuric  acid : 

K4Fe(CN)g  +  5H2SO4  =  6HCN  -f  FeSO^  +  4KHSO4. 

The  ferrous  sulphate  produced  reacts  with  more  ferrocyanide  to 
form  ferro-potassic  ferrocyanide,  FeKglFeCyg)  (see  p.  256),  which  is 
not  affected  by  dilute  acids ;  consequently  only  half  of  the  cyanogen 
present  is  converted  into  hydrocyanic  acid.  When  concentrated 
instead  of  dilute  sulphuric  acid  is  employed,  carbonic  oxide  and  not 
hydrocyanic  acid  is  obtained. 

2.  From  ammonium  formate  or  formamide  by  the  separation 
of  water  : 

H.0O.O(NH4)  =  H.CO.NH2  +  H2O  =  HON  +  2H2O. 

Hydrocyanic  is  therefore  the  nitrile  of  formic  acid. 

3.  Together  with  oil  of  bitter  almonds,  C^HgO,  and  grape 
sugar,  CgHjgOg,  through  the  decomposition  of  amygdalin 
under  the  influence  of  "  emulsin,"  (see  p.  294) : 

C20H27NO11  -f  2H2O  =  CNH  +  C^HgO  +  2C6H12O6. 

The  oil  of  bitter  almonds  and  its  aqueous  solution — (aqua  am  arum 
amygdalarum) — prepared  from  the  almonds  themselves,  consequently 
contain  HON. 

4.  By  the  action  of  ammonia  upon  chloroform  under  pressure  : 

CHCI3  +  NH3  rr  HCN  +  3HC1. 

For  other  syntheses,  see  p.  248. 


HYDROCYANIC  ACID. 


253 


Preparation.  From  yellow  prussiate  of  potash.  In  order  to 
obtain  the  anhydrous  acid,  the  vapours  are  dried  over  calcium 
chloride. 

Properties,  Colourless  liquid,  solidifying  at  -  15°.  Sp.  Gr. 
0-70.  B.  Pt.  26*5°.  It  has  a  peculiar  odour  and  produces  an 
unpleasant  irritation  in  the  throat,  is  miscible  with  water, 
etc.,  and  burns  with  a  violet  flame.  Like  potassium  cyanide, 
it  is  one  of  the  most  terrible  of  poisons.  When  absolutely 
pure  it  can  be  preserved  unchanged,  but  it  decomposes  in 
presence  of  traces  of  water  or  ammonia,  with  separation  of  a 
brown  mass  and  formation  of  ammonia,  formic  acid,  oxalic 
acid,  etc.  The  addition  of  minute  quantities  of  mineral  acids 
renders  the  aqueous  solution  more  stable. 

Hydrocyanic  acid  combines  with  nascent  hydrogen  to 
methylamine : 

HON  +  2H2  =  HCH2.NH2. 

With  hydrochloric  acid  it  forms  a  white  crystalline  product 
(HON  +  HCl),  which  appears  to  be  the  imido-chloride  of  formic  acid, 
CH — CC1=NH.  It  also  combines  with  many  metallic  chlorides  to 
crystalline  compounds  which  are  easily  decomposable. 

Hydrocyanic  acid  is  a  weak  monobasic  acid,  in  accordance 
with  the  mildly  acidifying  nature  of  the  cyanogen  radicle;  its 
salts  are  decomposed  even  by  carbonic  acid.  Its  constitutional 
formula,  H — C=N,  follows  from  its  relations  to  formic  acid 
and  chloroform.  In  some  reactions,  however,  it  yields  com- 
pounds which  are  derived  from  its  hypothetical  isomer 
=C=N — H  or  C=N — H.  Its  alcoholic  derivatives  each 
exist  in  two  isomeric  modifications,  nitriles  and  iso-nitriles, 
which  are  derived  from  the  two  atomic  groups  H — ON  and 
ON — H.  (See  table,  p.  250,  and  the  appendix  to  the  cyanogen 
group,  p.  265.) 

Hydrocyanic  acid  can  be  detected  by  converting  it  either  into 
Prussian  blue  or  into  ferric  sulphocyanide.  In  the  former  case  the 
solution  to  be  tested  is  treated  with  excess  of  caustic  soda  and  some 
ferrous  and  ferric  salt,  boiled,  and  acidified,  when  Prussian  blue  results  ; 
in  the  latter  the  solution  is  evaporated  to  dryness  along  with  a 
little  yellow  sulphide  of  ammonium,  the  residue  taken  up  with  water 
and  ferric  chloride  added,  when  the  blood-red  colour  of  ferric  sul[;lio- 
cyauide  is  obtained. 


254 


XII.  CYANOGEN  COMPOUNDS. 


Tri-hydrocyanic  acid,  (CNH)x,  results  from  the  polymerization  of 
hydrocyanic  acid  under  certain  specified  conditions.  It  forms  white 
acute-angled  crystals  which  go  back  into  hydrocyanic  acid  with  violence 
when  heated  above  180^.    Its  molecular  weight  is  still  unknown. 

Potassium  cyanide,  KCN.    For  formation^  see  p.  248. 
Preparation,    1.  Anhydrous  ferrocyanide  of  potassium  is 
heated  to  fusion : 

K4Fe(CN)6  =  4KCN  +  Fe  +  20  +  N^. 

In  order  to  prevent  the  decomposition  of  a  portion  of  the 
cyanide,  potash  may  be  added  to  the  melted  mass,  but  the 
product  will  in  this  case  contain  potassic  cyanate,  (Liebig's 
cyanide  of  potash.) 

2.  By  heating  potassium  in  cyanogen  gas. 

3.  By  the  combination  of  HON  with  KOH,  and  precipita- 
tion from  the  aqueous  solution  by  means  of  alcohol. 

Properties,  Colourless  deliquescent  cubes,  readily  soluble  in 
water  but  only  slightly  in  alcohol.  It  is  sold  in  sticks.  It 
absorbs  water  from  the  air  and  is  decomposed  by  the  carbonic 
acid  of  the  latter.  The  aqueous  solution  precipitates  nearly 
all  the  metallic  salts,  the  precipitates  redissolving  in  excess, 
with  formation  of  double  cyanides. 

Simple  Cyanides. 

Ammonium  cyanide,  NH4.CN".  White  deliquescent  mass.  It  is  also 
produced  by  the  passage  of  the  silent  electric  discharge  through  a 
mixture  of  marsh  gas  and  nitrogen. 

Mercuric  cyanide,  Hg(CN)2.  Colourless  prisms,  stable  in 
the  air  and  readily  soluble  in  water.    Excessively  poisonous. 

Silver  cyanide,  AgCN.  White  flocculent  precipitate,  closely 
resembling  chloride  of  silver  both  in  appearance  and  solubility. 

Double  Cyanides. 

The  double  cyanides,  which  are  produced  by  dissolving  the 
insoluble  metallic  cyanides  in  a  solution  of  cyanide  of  potas- 
sium, are  divided  into  two  classes.  The  members  of  the  one 
class  are  broken  up  again  on  the  addition  of  dilute  mineral 


POTASSIUM  FERRO-  AND  lERRIGYANIDES. 


acids  with  separation  of  the  insoluble  cyanide  and  formation 
of  hydrocyanic  acid,  e.^.  KCN  +  AgCN ;  2KCN  +  m{GN),. 
The  members  of  the  other  class  do  not  separate  hydrocyanic 
acid,  but  comport  themselves  as  salts  of  particular  acids;  to  the 
latter  belong,  in  especial,  potassic  ferrocyanide,  K^FeCy^, 
( =  4KCy  +  FeCyg),  and  potassic  ferricyanide,  KgFeCyg, 
( =  3KCy  +  FeCyg),*  which  yield  with  acids  hydro-ferro-  and 
hydro-ferricyanic  acids.  Many  salts  of  the  latter  acid  are 
not  decomposed  at  all  by  dilute  acids,  for  instance  Prussian 
blue,  but  they  are  by  caustic  potash  (which  converts  Prussian 
blue  into  Fe(0H)3  and  K^FeCyg). 

Potassium  ferrocyanide,  yellow  ^russiate  of  potash, 
K^FeCye  +  SHgO.  Formation.  1.  By  adding  excess  of 
potassium  cyanide  to  a  solution  of  ferrous  sulphate. 

2.  By  dissolving  iron  in  a  solution  of  cyanide  of  potassium, 
when  hydrogen  is  evolved,  thus : 

2KCN  +  Fe  +  2H,0  =  Fe(CN)2  +  2K0H  +  ; 
Fe(CN)2  +  4KCN  =  K4Fe(CN)e. 

Iron  is  therefore  previously  added  to  the  ''melt"  in  practical 
I  working  (see  p.  248,  3). 

'  It  forms  large  lemon-coloured  tetragonal  plates,  which  are 
I  stable  in  the  air  and  easily  soluble  in  water,  but  insoluble  in 
'  alcohol.  Concentrated  HCl  separates  Hydro-ferrocyanic  acid, 
H^FeCyg,  in  white  decomposable  needles.  With  a  solution  of 
CUSO4,  a  red-brown  precipitate  of  Cupric  ferrocyanide,  or 
Hatchetfs  brown,  CugFeCyg,  is  thrown  down,  and  with  solutions 
of  ferrous  and  ferric  salts  the  well  known  characteristic  precipi- 
tates.   Chlorine  oxidizes  it  to 

Potassium  ferricyanide,  red  ^russiate  of  potash,  EgFeCy^, 
thus : 

2K4FeCye  +  Cl^  =  2K3FeCye  +  2KC1. 

This  crystallizes  in  long  dark-red  monoclinic  prisms  which  are 
readily  soluble  in  water.  The  solution  decomposes  upon 
standing,  and  acts  as  a  strong  oxidizing  agent  in  the  presence 
of  alkali,  K^FeCyg  being  reproduced. 

*  For  the  sake  of  brevity,  iron  is  here  and  in  the  following  pages 
regarded  as  di-  and  trivalent. 


256  XII.  CYANOGEN  COMPOUNDS. 

Hydro-ferricyanic  acid,  HgFeCyg,  forms  brown  needles,  and 
is  easily  decomposed. 


FERRO-  AND  FERRI- CYANIDES  OF  IRON. 


Ferrocyanides. 

Ferricyanides. 

Ferrous  salts, 
Ferric  salts, 

Potassium-ferro-ferrocyanide, 
K2Fe"(FeCy6)^\  fromFeS04 
+  K4FeCyg  ;  white,  becom- 
ing rapidly  blue  in  the  air 
from  conversion  into 

Potassium-ferri-ferrocyanide, 
KFe^^HFeCye). 

Insoluble     Prussian  blue 
or      Williamson^  s  blue, 
Fe/HFeCy6)3,  from  FeClg 
+  K4FeCy6  ;  blue  powder 
with  a  copper  glance. 

KFe»'(FeCy6)i^  = 
Soluble  Prussian  blue,  from  : 
excess  of  ferro-  or  ferri-cyan 

TurnhuWs  blue, 
Fe/(FeCy6)2"S  from 
FeS04  +  KsFeCye. 

(FeClg  +  K3FeCy6  give  no 
precipitate,    but  only 
a  brown  colouration. ) 

KFe"(FeCy6)"'  = 
erric  or  ferrous  salts  and 
ide  of  potassium. 

The  formation  of  Prussian  blue  was  first  observed  by  Diesbach  soon 
after  the  year  1700. 

As  regards  the  constitution  of  hydro-ferro-  and  hydro-ferricyanic 
acids,  one  may  make  the  assumption  that  they  contain  the  trivalent 
radicle  (C3N3)"',  *'  tricyanogen,"  of  cyanuric  acid  (see  p.  140)  : 

Potassium  ferrocyanide.  Potassium  ferricyanide. 

TurnbulFs  blue. 

When  ferrocyanide  of  potassium  is  oxidized  by  nitric  acid, 
there  is  formed  Nitro-prussic  acid,  whose  sodium  salt, 
FeCy5(NO)Na2  +  2H2O,  crystallizes  in  red  prisms  soluble  in 
water  and  forms  a  valuable  reagent  for  the  detection  of 
sulphuretted  hydrogen,  an  alkaline  solution  yielding  with  the 
latter  a  splendid  but  tiansietit  purple-blue  colouration. 


CYANOGEN  CHLORIDE;  CYANIC  ACID. 


257 


B.  Halogen  Compounds  of  Cyanogen. 

Cyanogen  chloride,  CN.Cl,  {Berthollet).  Colourless  con- 
densible  gas  of  a  most  obnoxious  pungent  odour,  somewhat 
soluble  in  water.  B.  Pt.  of  its  liquid  -  12°.  It  is  prepared 
by  the  action  of  chlorine  upon  mercuric  cyanide  or  upon  dilute 
aqueous  hydrocyanic  acid,  thus  : 

CNH  +  CI2  =  CNCl  +  HCl. 

It  polymerizes  readily  to  cyanuric  chloride,  and  yields  potassic 
chloride  and  cyanate  with  aqueous  potash,  appearing  thus  as 
the  chloride  of  cyanic  acid  : 

CN.Cl  +  2K0H  =  CN.OK  +  CIK  +  H^O.  " 

Cyanogen  bromide,  CNBr.  Analogous  to  the  chloride.  Transparent 
prisms. 

Cyanogen  iodide,  CNTI.  Beautiful  white  prisms,  smeUing  intensely 
both  of  cyanogen  and  iodine,  and  subliming  with  the  utmost  ease. 
Very  poisonous.    Prepared  from  mercuric  cyanide  and  iodine. 

Cyanuric  chloride,  tri-chloro-cyanogen,  (CN)3Cl3.  This 
polymer  is  obtained  from  cyanogen  chloride,  or  from  hydro- 
cyanic acid  and  chlorine  in  ethereal  solution.  It  forms  beauti- 
ful white  crystals,  of  an  unpleasant  pungent  odour.  M.  Pt. 
140°,  B.  Pt.  190°.  Boiling  water  decomposes  it  with  formation 
of  hydrochloric  acid  and  cyanuric  acid,  (CN)3.(OH)3,  of  which 
latter  it  appears  as  the  chloride.  It  contains  the  trivalent 
radicle  (CN)3'"  =  tri-cyanogen,  (see  Cyanuric  acid). 


0.  Cyanic  and  Cyanuric  acids. 

Cyanuric  acid  is  formed  when  urea  is  heated,  either  alone  or 
in  a  stream  of  chlorine  gas  ;  by  subjecting  it  to  dry  distillation 
and  condensing  the  vapours  evolved  in  a  freezing  mixture,  one 
obtains  Cyanic  acid,  CNOH,  as  a  mobile  liquid  of  a  pungent 
odour : 

C3N3O3H3  =  3CN0H. 

It  is  exceedingly  unstable ;  when  taken  out  of  the  freezing 
mixture  it  changes,  with  explosive  ebullition,  into  the  poly- 

(506)  R 


258 


XII.  CYANOGEN  COMPOUNDS. 


meric  Cyamelide,  (CONH)^,  a  white  porcelain-like  mass  which 
goes  into  cyanic  acid  again  upon  heating.  Cyanic  acid  com- 
bines with  ammonia  to  cyanate  of  ammonium. 

Potassium  cyanate,  CNOK,  frequently  also  termed  potas- 
sium isocyanate,  is  prepared  by  fusing  potassic  cyanide  or 
yellow  prussiate  of  potash  with  PbOg  or  MnOg  :  (CNK  +  0 
=  CNOK).   White  plates,  readily  soluble  in  water  and  alcohol. 

Ammonium  cyanate,  CN0(NH4),  forms  a  white  crystalline 
mass,  and  is  of  especial  interest  on  account  of  the  readiness 
with  which  it  changes  into  the  isomeric  urea,  CONgH^. 

When  hydrochloric  acid  is  added  to  these  salts,  there  result 
— instead  of  free  cyanic  acid— its  products  of  saponification, 
CO2  and  NH3  : 

CONH  +  H2O  =  CO2  +  NH3. 

This  decomposition  is  avoided  by  the  addition  of  dilute  acetic 
acid  (instead  of  hydrochloric),  but  in  the  latter  case  the 
cyanic  acid  changes  into  its  polymer  cyanuric  acid,  the 
hydrogen^otassium  salt  of  the  latter  slowly  crystallizing  out. 


From  cyanic  acid  are  derived  two  isomeric  classes  of  alco- 
holic derivatives,  by  the  replacement  of  the  hydrogen  by 
alcohol  radicles.  The  derivatives  which  are  constituted  on 
the  type  N=C.OR  are  termed  the  normal,  and  those  on  the 
type  0=C=NR  the  iso-compounds. 

I.  When  potassium  cyanate  is  distilled  with  ethyl  iodide  or, 
better,  with  potassium  ethyl-sulphate,  there  is  obtained 

Ethyl  iso-cyanate  or  cyanic  ether,  CO.NC2H5,  a  colourless 
liquid  of  suffocating  odour,  which  boils  unchanged  at  60°  and 
is  decomposed  by  water.  It  does  not  possess  the  properties  of 
a  compound  ether,  but  is  broken  up  by  alkalies  or  acids  into 
ethylamine  and  carbon  dioxide,  thus  ; 

CONC2H5  +  H2O  =  CO2  +  NH2.C2H5. 
Water,  which  acts  in  a  similar  manner,  gives  rise  to  the 
more  complicated  urea  derivatives ;  ammonia  and  amine  bases 


CYANIC  AND  CYANURIC  ACIDS. 


259 


also  produce  derivatives  of  urea  (p.  272),  and  alcohol  yields 
derivatives  of  carbamic  acid  (p.  270). 

Constitution, — The  formation  of  ethylamine  proves  that  the  N  of  the 
cyanic  ether  is  linked  directly  to  the  alcohol  radicle,  so  that  the  consti- 
tution is  :  0=C=N.C2H5.  It  is  questionable,  however,  whether  free 
cyanic  acid  and  cyanate  of  potassium  possess  analogous  constitutions, 
since  frequent  observations  have  shown  that  the  normal  cyanic  com- 
pounds readily  change  into  the  iso-(see  below);  theoretical  considerations 
indeed  make  it  more  probable  that  cyanic  acid  has  the  constitution 
N=C — OH,  according  to  which  it  appears  as  the  normal  acid,  with 
cyanogen  chloride  as  its  chloride.    Potassium  cyanate  would  then  be 

]sr=c— 0— K. 

II.  The  so-called  cyan-etholines,  which  are  said  to  result  from  the 
action  of  cyanogen  chloride  upon  sodium  alcoholates,  are  regarded  as 
isomeric  with  these  cyanic  ethers,  e.g. 

Cyan-etholine,  CN.OCgBIs.  From  this  mode  of  formation,  the  cyan- 
etholines  appear  to  be  derivatives  of  normal  cyanic  acid,  CN.OH  ; 
their  chemical  nature  is,  however,  not  yet  sufficiently  investigated. 

Cyanuric  acid,  C3N3O3H3,  =  (CN)3(OH)3  (Scheele).  The 
formation  of  cyanuric  acid  by  heating  urea,  already  mentioned 
on  p.  257,  is  easily  understood  when  one  remembers  that  it  is 
made  up  of  the  constituents  of  cyanic  acid  and  ammonia,  so 
that,  when  the  latter  is  split  off,  the  former  becomes  free  and 
then  polymerizes.  Cyanuric  acid  forms  transparent  prisms 
which  contain  2  mols.  HgO  of  crystallization  and  weather  in 
the  air,  and  which  are  readily  soluble  in  hot  water.  It  is  a 
tribasic  acid.  The  sodium  salt  is  sparingly  soluble  in  cone. 
NaOH ;  the  copper  salt  possesses  a  characteristic  beautiful 
violet  colour.  Upon  prolonged  boiling  with  hydrochloric  acid 
it  is  saponified  to  COg  and  NH3,  while  phosphorus  penta- 
chloride  converts  it  into  cyanuric  chloride,  the  acid  being 
regenerated  from  this  by  water. 

Cyanuric  acid  also  gives  rise  to  two  isomeric  classes  of  alcoholic 
derivatives,  viz.  : 

1.  The  Normal  cyanuric  ethers,  e.g.  C3N3(OC2H5)3  (a  colourless 
liquid),  which  result  from  the  polymerization  of  the  cyan-etholines  and 
also  by  the  action  of  methyl  iodide  etc.  upon  cyanurate  of  silver  at  the 
ordinary  temperature.    They  easily  change  into  the  isomeric 

2.  Iso-cyanuric  ethers  or  tri-carbimido  ethers,  e.g.  C303(NC2Hg)3, 
colourless  liquids  which  frequently  result  instead  of  the  cyanic  ethers, 


260 


XII.  CYANOGEN  COMPOUNDS. 


for  example,  on  the  distillation  of  cyanurate  with  ethyl-sulphate  of 
potassium.  They  are  further  formed  by  the  polymerization  of  the  iso- 
cyanic  ethers,  being  thus  obtained  as  bye-products  in  the  preparation  of 
the  latter. 

The  normal  compounds  are  broken  up  by  saponification  with  the 
formation  of  alcohol,  and  the  isomers  with  formation  of  ethylamine. 

The  constitution  of  cyanuric  acid  follows  from  its  relation  to  cyanuric 
chloride  as  (CN)3(OH)3,  and  that  of  the  alkyl  derivatives  from  their 
behaviour  upon  saponification.  The  normal  compounds  therefore 
contain,  like  cyanuric  chloride,  the  trivalent  radicle  tri-cyanogen, 
(CN)3,  whose  N-  and  C-atoms  one  assumes  to  be  linked  to  each 
other  alternatively  by  single  and  double  bonds  in  a  closed  ring," 
while  the  iso-cyanic  ethers  are  to  be  regarded  as  derived  from  a  hypo- 
thetical original  substance  consisting  of  three  CO-  and  NH-groups 
joined  together  in  the  form  of  a  ring.  (Cf,  A.  W,  Hofmann,  B.  18, 
2755,  3261  ;  also  Benzene  derivatives)  : 


OH 
I 


(OC2H5) 
If  N 


C1_C^  ,C— CI  HO— C 
Cyanuric  chloride. 


Cyanuric  acid. 


C-OH    (CsHgO-C  C-IOC^H,) 


Cyanuric  ether. 


O 


oc.  ,co 
(C2H5) 

Isocyanuric  ether. 

In  addition  to  cyanuric  acid  and  cyamelide,  various  other  polymers 
of  cyanic  acid  have  been  described,  but  only  some  of  them  have  been 
closely  studied.    (Cf.  among  others,  J.  pr.  Ch.  32,  461.) 

Further,  in  the  aromatic  series,  derivatives  of  a  Di-isocyanic  acid, 
(CO)2.(lSrH)2,  are  known,  (B.  18,  764). 


THIOCYANIC  ACID. 


261 


D.  Thiocyanic  Acid  and  its  Derivatives. 

Potassium  thiocyanate,  -sulphocyanate,  -sulphocyanide, 
-rhodanide,  CNSK.  Potassium  cyanide  not  only  combines 
readily  with  oxygen  to  cyanate  but  also  with  sulphur  to  thio- 
cyanate, either  when  fused  with  sulphur  or  when  its  solution 
is  evaporated  with  yellow  sulphide  of  ammonium  : 

KCN  +  S  =  CNSK. 

It  is  prepared  hy  fusing  yellow  prussiate  of  potash  with 
sulphur  and  potashes.  It  forms  long  colourless  deliquescent 
prisms,  extremely  soluble  in  water  with  absorption  of  much 
heat,  and  also  easily  soluble  in  hot  alcohol. 

Ammonium  thiocyanate,  ammonium  rhodanide,  CNS(NH4), 
results  upon  warming  a  mixture  of  carbon  bisulphide,  concen- 
trated ammonia  and  alcohol  (Millon),  di-thiocarbamate  and 
tri-thiocarbonate  of  ammonia  being  formed  as  intermediate 
products  (see  p.  275) : 

CS2  +  NH3  =  CNSH  +  H^S. 

Colourless  deliquescent  plates,  readily  soluble  in  alcohol. 
Upon  being  heated  to  130°-140°,  it  is  partially  transformed 
into  the  isomeric  thio-urea,  just  as  ammonium  cyanate  is  into 
ordinary  urea.  It  precipitates  silver  thiocyanate,  CNSAg, 
(white)  from  solutions  of  silver  salts,  and  is  therefore 
employed  in  the  titration  of  silver,  with  ferric  sulphate  as 
indicator ;  and  it  gives  with  ferric  salts  a  dark  blood-red  colour- 
ation of  ferric  thiocyanate,  Fe2(CNS)(> l^HgO  This  last 
reaction  is  exceedingly  delicate. 

Mercurous  thiocyanate,  Hg2(CNS)2,  is  a  white  powder  insoluble  in 
water,  which  increases  enormously  in  volume  upon  being  burnt, 
(Pharaoh's  serpents).  The  Barium  salt  is  used  in  printing  with  alizarin 
red.  The  free  Thiocyanic  acid,  CNSH,  is  a  pale  yellow  liquid  with  a 
pungent  odour  resembling  that  of  glacial  acetic  acid,  miscible  with 
water,  and  boiling  at  102°.  It  is  prepared  either  by  leading  HgS  over 
the  warmed  mercury  salt  or  into  its  aqueous  solution,  and  also  by  dis- 
tilling the  potassium  salt  with  dilute  sulphuric  acid.  It  is  only  stable 
in  a  freezing  mixture  or  in  aqueous  solution,  readily  decomposing  other- 
wise with  formation  of  Persulphocyanic  acid,  CgNgSgHg  (yellow  crystals). 


262 


XII.  CYANOGEN  COMPOUNDS. 


Concentrated  sulphuric  acid  decomposes  the  thiocyanates 
with  formation  of  carbon  oxy-sulphide  :  CNSH  +  HgO 
=  COS  +  NH3 ;  sulphuretted  hydrogen  decomposes  them  into 
carbon  bisulphide  and  ammonia :  CNSH  +  HgS  =  CSg  +  NH3. 

Cyanogen  sulphide,  (CN)2S,  is  to  be  regarded  as  the  thio-anhydride 
of  thiocyanic  acid  ;  it  is  prepared  from  cyanogen  iodide  and  silver  thio- 
cyanate, and  forms  readily  soluble  plates  of  sharp  odour. 


Just  as  in  the  case  of  cyanic  acid,  so  are  there  derived  from 
thiocyanic  acid  two  isomeric  classes  of  alcoholic  derivatives, 
by  the  replacement  of  hydrogen  by  alcohol  radicles. 

I.  Compound  ethers  of  thiocyanic  acid  result  from  the 
entrance  of  alcoholic  radicles  in  the  place  of  the  hydrogen  of 
the  acid. 

Ethyl  thiocyanate,  CN.SCgH^,  is  obtained  either  (1)  by  the 
distillation  of  potassium  ethyl-sulphate  with  potassium  thio- 
cyanate, or  (2)  by  the  action  of  cyanogen  chloride  upon 
a  mercaptide.  It  is  a  colourless  liquid  with  a  peculiar  pungent 
odour  of  leeks,  and  almost  insoluble  in  water.  B.  Pt.  142°. 
Alcoholic  potash  saponifies  it  in  the  normal  manner  with 
reproduction  of  potassium  thiocyanate ;  in  other  reactions, 
however,  the  alcoholic  radicle  remains  united  to  the  sulphur. 

Thus  nascent  hydrogen  reduces  it  to  mercaptan,  and  fuming  nitric 
acid  oxidizes  it  to  ethyl-sulphonic  acid. 

It  follows  from  mode  of  formation  (2)  and  also  from  the  reactions  of 
the  thiocyanic  ethers  that  the  sulphur  in  them  is  linked  to  the  alcohol 
radicle.  Consequently  in  the  salts  it  is  linked  to  the  metal  in  question, 
and  in  the  free  acid  to  hydrogen.  We  have  therefore  the  following 
constitutional  formulae  ; 


AUyl  thiocyanate,  CN.SC3H5.  Colourless  liquid  smelling  of  leeks. 
B.  Pt.  161°.    Changes  upon  distillation  into  the  isomeric  mustard  oil. 


II.  Isomeric  with  the  thiocyanic  ethers  are  the  mustard 
oils  Senfole.") 
AUyl  iso-thiocyanate,  common  mustard  oil,  CS  :  N.C3H5,  is 


N=C— SH 


N=C— SK  N^C— SC2H5 

Potassium  thiocyanate.      Ethyl  thiocyanate. 


Thiocyanic  acid. 


THE  ISO-THIOCYANATES. 


263 


prepared  by  distilling  the  seeds  of  black  mustard  (Siiiapis 
niger)  with  water.  It  is  a  liquid  sparingly  soluble  in  water  and 
of  exceedingly  pungent  odour,  which  produces  blisters  on  the 
skin.  B.  Pt.  151°.  It  results  on  distilling  allyl  thiocyanate, 
by  a  molecular  rearrangement,  and  it  is  also  obtained  by  the 
action  of  carbon  bisulphide  upon  the  corresponding  primary 
amine,  allylamine,  thus  : 

CS2  +  NH2.C3H5  =  CS  :  N.C3H5  +  H^S. 

This  reaction  does  not,  however,  proceed  exactly  as  indicated  in  the 
above  equation,  there  being  first  formed  the  allylamine  salt  of  allyl- 
di-thiocarbaniic  acid,  which  is  changed  into  allyl  iso-thiocyanate  upon 
distillation  with  mercuric  chloride.    (See  di-thiocarbamic  acid,  p.  276. ) 

Ethyl  iso-thiocyanate,  C2H5N.CS,  (B.  Pt.  134°),  and  Methyl  iso-thio- 
cyanate, CH3N.CS,  (solid,  M.  Pt.  34°,  B.  Pt.  119°),  etc.,  closely 
resemble  the  allyl  compound,  and  are  obtained  in  an  analogous  manner 
by  the  action  of  carbon  bisulphide  upon  ethylamine,  methylamine,  etc. 

The  mustard  oils  also  result  from  the  distillation  of  alkylated  thio- 
ureas (p.  277)  with  syrupy  phosphoric  acid  {Hofmann,  B.  15,  985),  or 
with  concentrated  hydrochloric  acid.  They  break  up  on  being  saponi- 
fied, with  reproduction  of  the  primary  amines  from  which  they  can  be 
prepared  : 

CS.NC3H5  +  2H2O  =  NH2.C3H5  +  H2S  +  CO2. 

They  are  connected  with  the  thio-ureas  by  various  reactions,  and 
also  with  the  cyanic  ethers,  since  in  the  latter  0  can  be  replaced  by  S, 
but  in  the  mustard  oils,  on  the  contrary,  S  by  0. 

The  constitution  of  the  mustard  oils  follows  from  their  relation  to  the 
primary  amines,  the  alkyl  being  linked  to  nitrogen  in  both  classes  of 
compounds  ;  the  constitutional  formula  of  methyl  iso-thiocyana.te  is 
therefore  S=C=N — CH3.  Iso-thiocyanic  acid,  SC=NH,  is  itself 
unknown. 

Polymers.  Dithio-dicyanic  acid,  CgNgSgHg.  The  potassium  salt  of 
this  polymer  has  been  described,  but  little  is  known  about  it. 

Thio-cyanuric  acid,  (C3N3)(SH)3,  is  a  tribasic  acid.  Yellow  powder. 
The  primary  sodium  salt,  C3No(SH)2SNa,  crystallizes  well.  It  is  formed 
e.g.  by  the  action  of  cyanuric  chloride  upon  sodium  sulphide,  whence 
its  constitution  follows.  Its  Tri-methyl  ether  results  along  with 
methyl  iso-thiocyanate  upon  heating  methyl  thiocyanate  to  180°,  by 
the  polymerization  and  subsequent  molecular  transformation  of  the 
latter. 


264 


XII.  CYANOGEN  COMPOUNDS. 


E.  Oyanamide  and  its  Derivatives. 

Cyanamide,  CN.NHg,  {Bineau),  is  formed  : 

1.  By  leading  cyanogen  chloride  into  an  ethereal  solution  of 
ammonia  : 

CNCl  +  2NH3  =  CN.NH2  +  NH4CI. 

2.  By  the  action  of  HgO  upon  thio-urea  in  aqueous  solution, 
("  desulphurization  ")  : 

NH2— CS— NH2  =  NC.NH2  +  H2S. 

Colourless  crystalline  hygroscopic  mass,  readily  soluble  in 
water,  alcohol  and  ether.  M.  Pt.  40°.  When  heated  to  150°, 
it  changes  into  the  polymeric  melamine  with  explosive 
ebullition.  In  the  same  way  it  easily  goes  into  the  polymeric 
dicyan-diamide  on  evaporating  its  solution  or  allowing  it  to 
stand.  Dilute  acids  cause  it  to  take  up  the  elements  of  water, 
with  formation  of  urea:  CN.NHg  +  HgO  ^  CONgH^;  and 
it  combines  in  an  analogous  manner  with  sulphuretted 
hydrogen  to  thio-urea.  When  heated  with  ammonia  salts  it 
yields  salts  of  guanidine. 

Cyanamide  behaves  as  a  w^eak  base,  forming  crystalline 
easily  decomposable  salts  with  acids  and,  at  the  same  time,  as 
a  weak  acid,  yielding  a  sodium  salt,  CN.NHNa,  a  lead  and  a 
silver  salt,  etc.  The  last  is  a  yellow  powder  and  has  the 
composition  CNgAgg. 

Cyanamide  also  gives  rise  to  two  isomeric  series  of  alcoholic  deriva- 
tives, by  the  replacement  of  the  hydrogen  by  alkyl. 

I.  Methyl-  and  Ethyl- cyanamides  are  prepared  e.g.  from  methyl-  and 
ethyl-thio-urea.  Di-ethyl-cyanamide,  CN2(C2H5)2,  is  obtained  by  treat- 
ing silver- cyanamide  with  ethyl  iodide.  Acids  saponify  it  to  CO2,  NH3 
and  NH(C2H5)2,  hence  it  possesses  the  constitution  N^C — N(C2H5)2  : 

N=C-N(C2H5)2  +  2H2O  =  NH3  -f  CO2  +  NH(C2H5)2. 

From  this  it  follows  that  cyanamide  has  most  probably  the  constitu- 
tion which  corresponds  with  its  name,  viz.,  N=C — NHg. 

II.  Other  cyanamide  derivatives,  which  are  chiefly  known  in  the 
aromatic  series,  spring  from  a  hypothetical  isomer  of  cyanamide,  viz., 
Carbo-di-imide,  NH=C=NH  ;  for  instance,  Diphenyl-carbo-di-imide, 
CN2(C6H5)2.  Boiling  with  acids  likewise  decomposes  them  into  OOg 
and  an  amine,  but  the  latter  can  only  be  a  primary  one. 


ISOMERISM  IN  THE  CYANOGEN  GROUP. 


265 


Polymers.  Dicyan-diamide,  parame^  C2N4H4  (p.  264).  Crystallizes 
in  beautiful  broad  needles  or  prisms,  and  has  probably  the  constitution 

N=C— NH— C^^^  ,  (B.  19,  440).  Like  cyanamide,  it  yields  mela- 
mine  when  strongly  heated. 

Melamine,  cyanuramide,  CgNgHg,  (Liebig^  1838),  forms  glancing 
rhombic  octahedra,  insoluble  in  alcohol  and  ether,  and  possesses  basic 
properties.  When  it  is  boiled  with  acids,  the  NHg-  groups  are  succes- 
sively replaced  by  OH  with  the  formation  of  Ammeline,  (CN)3(N"H2)20H, 
Ammelide,  (CN)3N"H2(OH)2,  and  finally  cyanuric  acid,  (CN)3(OH)3. 
Melamine  has  therefore  the  constitution  (CN)3(NH2)3,  =  tricyan- 
triamide. 

Further,  alkylated  melamines  are  derived  from  the  latter  by  the 
replacement  of  hydrogen  by  alkyl,  and  in  addition  to  these  there 
exists  an  isomeric  class  of  compounds  of  which  the  hypothetical 
*'Iso -melamine,"  [C(NH)]3(NH)3,  is  the  basis.  To  this  class  belong  the 
polymerization  products  of  the  alkyl  cyanamides.  The  following  con- 
stitutional formulae  are  ascribed  to  these  two  series,  (R= Alcohol 
radicle) : 

/^\ 

and  RN"^  RN 

I  II  II 

Melamines.  Iso-melamines. 
For  particulars  see  A.  W.  Hofmann,  B.  18,  2755,  3217, 


P.  Appendix.    Theoretical  Considerations  as  to 
isomerism  in  the  Cyanogen  Group. 

As  has  already  been  explained,  there  are  derived  from  hydrocyanic 
acid,  cyanic  acid,  thiocyanic  acid  and  cyanamide,  and  also  from  their 
polymers,  two  classes  of  isomeric  alcoholic  derivatives  which  differ 
sharply  from  one  another  in  their  products  of  decomposition.  They 
correspond,  properly  speaking,  to  two  isomeric  mother  substances — 
the  "normal  "  and  *'pseudo  "  forms  {Ad.  Baeyer) — only  one  of  which, 
however,  is  known  in  the  free  state,  viz.,  the  normal  compound,  (cf. 
Hofmann,  loc.  cit.).  The  fact  that  the  isomeric  form  has  never  been 
obtained  may  be  explained  by  assuming  that  it  represents  an  unstable 
state  of  equilibrium  of  the  atoms,  and  that,  when  attempts  are  made  to 


266 


XIII,  DERIVATIVES  OF  CARBONIC  ACID. 


prepare  it,  it  immediately  undergoes  molecular  transformation  into  the 
other,  stable,  form.  When  the  hydrogen  is  replaced  by  alkyl,  both 
varieties  of  atomic  groups  are  in  most  cases  capable  of  existence, 
although  even  here  also  a  difference  in  stability  is  observed,  the 
normal  compounds  changing  very  readily  into  the  iso-  (or  pseudo-)  com- 
pounds. In  consequence  of  this  one  obtains  the  iso-cyanic  ether  directly 
from  potassium  cyanate  instead  of  the  normal  one,  allyl  thiocyanate 
readily  changes  into  the  iso- thiocyanate,  and  iso-cyanuric  ether  is 
usually  got  instead  of  cyanuric,  etc.,  etc.  It  is  also  conceivable  that 
the  mother  substances  may  possess  both  the  above  constitutional 
formulae,  i.e.  that,  by  the  wandering  of  an  atom  of  hydrogen,  their 
atoms  may  sometimes  arrange  themselves  in  the  one  and  sometimes  in 
the  other  form,  and  that  they  may  accordingly  show  the  reactions  of 
either,  ("  Tautomerism  ").  The  discussion  upon  this  point  is  still  going 
on.  (Cf.  Laar,  B.  18,  648;  19,  730.)  Among  other  compounds 
regarding  which  considerations  of  this  nature  have  been  advanced,  may 

be  specially  mentioned  thio-urea,  CS(NH2)2  or  C(NH)||^^2  (p^  277), 

thiamides  of  monobasic  acids,  R — CS.NHg  or  R — ^^S^  ^P*  ^^^)» 

aceto-acetic  ether,  CH3-CO-CH2-CO2R  or  CH3-C(OH)=CH-C02R, 
succino-succinic  ether,  phloroglucin,  isatin,  carbostyril,  etc.  One  of 
the  formulae  in  question  of  these  substances  is  convertible  into  the 
other  simply  by  the  wandering  of  a  hydrogen  atom.  It  has  been  proved 
that  many  of  these  compounds  react  in  a  manner  which  corresponds  as 
well  with  the  one  formula  as  with  the  other.  When  a  "  change  in  the 
bonds"  of  such  tautomeric"  substances  occurs,  it  is  termed  *'desmo- 
tropism,"  {Hantzsch  and  Herrmann,  B.  20,  2081).  In  the  case  of  the 
derivatives  of  succino-succinic  ether,  these  desmo tropic  states"  are 
coincident  with  changes  in  physical  properties  ;  the  compounds  are 
sometimes  coloured,  sometimes  colourless,  and  at  the  same  time  one 
of  the  states  is  unstable,  the  other  being  stable. 


XIII.  OARBONIO  AOID  DERIVATIVES. 

Carbonic  acid  is  a  dibasic  acid,  forming  two  series  of 
salts,  e.g,  Na2C03  and  NaHCOg.    The  hydrated  acid  itself, 
OH 

CO3H2,  =  C)=C)<^Qjj,  is  unknown,  but  may  be  supposed  to 
exist  in  the  aqueous  solution. 

Its  empirical  formula  shows  carbonic  to  be  the  lowest  oxy-acid 
CnH2n03,  i.  6.  it  is  homologous  with  glycollic  acid  and  may  be  looked  upon 


ETHERS  OF  CARBONIC  ACID. 


267 


as  oxy-formic  acid.  Its  dibasic  nature  is  explained  by  the  carbonyl 
group  apparently  extending  its  acidifying  character  over  both  hydroxyls 
equally.  Since  the  latter  are  both  linked  to  one  carbon  atom,  the  non- 
existence of  the  free  hydrate  is  readily  understood  (see  p.  131,  etc.). 

The  salts  of  carbonic  acid  and  those  of  several  of  its  deriva- 
tives, such  as  carbon  bisulphide,  CSg,  and  carbon  oxy-sulphide, 
COS,  have  been  already  treated  of  under  inorganic  chemistry. 
But  there  still  remain  for  description  the  compound  ethers, 
chlorides  and  amides  of  carbonic  acid,  two  series  of  which 
exist,  acid  and  neutral,  as  in  the  case  of  all  the  dibasic  acids, 
CnH2„_204.  The  neutral  compounds  are  well  characterized 
and  are  very  similar  to  those  of  oxalic  or  succinic  acid ;  the 
acid  compounds  on  the  other  hand  are  unstable  in  the  highest 
degree  when  in  the  free  state,  and  are  known  almost  only  as 
salts.  Many  mixed  derivatives  have  also  been  prepared,  e,g, 
carbamic  ether,  CO(NH2)(OC2H5),  analogous  to  oxamethane 
(p.  233). 

Summary, 


Neutral 
derivatives. 

Ethyl  carbonate. 

COClg 
Carbonyl  chloride. 

CO(NH2)2 
Urea. 

Acid 
derivatives. 

CO(OC2H5).OH 
Ethyl  carbonic  acid. 

C0(C1)(0H) 
Chloro-carbonic  acid. 

C0(NH2)(0H) 
Carbamic  acid. 

Mixed 
derivatives. 

CO(Cl)(OC2H5) 
Chloro-carbonic  ether. 

CO(NH2)(OC2H5) 
Urethane. 

The  modes  of  formation  of  these  compounds  are  for  the  most  part 
exactly  analogous  to  those  of  the  corresponding  derivatives  of  the 
monobasic  acids  and  of  oxalic  acid. 


A.  Ethers  of  Carbonic  Acid. 

Ethyl  carbonate,  GO{OG^^^,  is  formed  : 

1.  By  the  action  of  ethyl  iodide  upon  silver  carbonate  ; 


268  XIII.  DERIVATIVES  OF  CARBONIC  ACID. 


2.  By  the  action  of  alcohol  upon  chloro-carbonic  ether,  and 
therefore  indirectly  from  carbon  oxychloride  and  alcohol : 

CO(OC2H5)Cl  +  C2H5OH  =  COiOG^R,)^  +  HCl. 

It  is  a  neutral  liquid  of  agreeable  odour,  lighter  than  water 
and  insoluble  in  the  latter.    B.  Pt.  126°. 

Analogous  Methyl-,  Propyl-,  etc.  carbonates  are  known,  and  also 
ethers  containing  two  different  alcohol  radicles.  It  is  a  matter  of  no 
consequence  which  of  these  radicles  is  introduced  first  into  the  molecule, 
a  proof  of  the  equal  valency  of  the  two  hydroxyls. 

Ethyl-carbonic  acid,  CO(002H5)(OH),  corresponds  exactly 
with  ethyl-sulphuric,  but  is  much  less  stable  and  only  known 
in  its  salts. 

Potassium  ethyl-carbonate,  CO(OC2H5)(OK),  results  upon  passing 
CO2  into  an  alcoholic  solution  of  potassium  ethylate  :  COg  +  KOC2H5 
=  003(02115) K.  It  crystallizes  in  glancing  mother-of-pearl  plates,  but 
is  decomposed  by  water  into  potassium  carbonate  and  alcohol. 

B.  Chlorides  of  Carbonic  Acid. 

Carbon  oxy-chloride,  carbonyl  chloride,  johosgene,  COClg, 
(/.  Davy).  This  compound  is  analogous  to  succinyl  chloride, 
03114(0001)2,  and  to  sulphuryl  chloride,  SOgOlg.  It  is  ob- 
tained by  the  direct  combination  of  carbonic  oxide  and 
chlorine  in  sunlight,  etc.,  and  also  by  the  oxidation  of  chloro- 
form by  means  of  chromic  acid.  Oolourless  gas,  condensing 
to  a  liquid  below  4-8°,  of  exceptionally  suffocating  odour. 
Soluble  in  benzene.  As  an  acid  chloride  it  decomposes 
violently  with  water  into  OO2  and  HOI.  It  therefore  trans- 
forms hydrated  acids  into  their  anhydrides,  with  separation  of 
water,  and  converts  aldehyde  into  ethylidene  chloride.  It 
yields  urea  with  secondary  amines  of  the  fatty  series,  and 
carbamic  chlorides  with  secondary  amines  of  the  aromatic.  Is 
employed  in  the  preparation  of  salicylic  acid. 

Chloro-carbonic  acid,  OOOl(OH),  the  acid  chloride  of  car- 
bonic acid  analogous  to  chlor-oxalic  acid  (p.  232),  has  too 
great  a  tendency  to  break  up  into  OO2  and  HOI  to  allow  of  its 


AMIDP]S  OF  CARBONIC  ACID. 


269 


existence  either  in  the  free  state  or  in  that  of  salts.  As  a 
monobasic  acid,  however,  it  forms  ethers,  e.g.  Chloro-carbonic 
ether,  CO(Cl)(OC2H5)  (  -  chloro-formic  ether,  CI— CO.OCgH^), 
Avliich  results  from  the  action  of  carbon  oxy-chloride  upon 
alcohol,  (Dumas,  1833) : 

COCI2  +  C2H5OH  =  COCl(OC2H5)  +  HCl. 
This  is  a  volatile  liquid  of  very  pungent  odour,  which  boils 
at  94°.    It  reacts  as  an  acid,  chloride,  being  decomposed  by 
water,  and  is  therefore  specially  fitted  to  effect  the  synthetical 
entrance  of  the  carboxyl  group  into  many  compounds. 

The  corresponding  Methyl-  etc.  ethers  are  very  similar. 

0.  Amides  of  Carbonic  Acid. 

The  neutral  amide  of  carbonic  acid  is  urea  or  carbamide, 
the  acid  amide  or  aminic  acid  is  carbamic  acid.  Imido-carbonic 
OH 

acid,  C(NH)qjj,  would  be  an  imide  of  carbonic  acid,  but  it  is 

only  known  in  its  derivatives,  (Sandmeyer,  B.  19,  862). 

The  hypothetical  form  of  cyanic  acid,  CO=NH  (see  table,  p.  250), 
would  also  be  an  imide  of  carbonic  acid,  and  that  of  cyanamide,  C(NH)2, 
a  di-imide,  while  cyanic  acid  itself  is  to  be  regarded  as  a  half  nitrile, 
with  cyanamide  as  its  amide.  The  recently  prepared  Imido-carbonic 
ether,  C.NH(O.C2Hg)2,  (B.  19,  864),  is  an  imido-compound  of  carbonic 
acid.  The  amidine  of  carbonic  acid  is  guanidine.  The  "  ortho-amide  " 
of  carbonic  acid,  which  would  possess  the  formula  C(NH2)4,  is  un- 
known ;  when  it  might  be  expected  to  be  formed,  guanidine  and 
ammonia  result  instead. 

The  modes  of  formation  of  urea  and  of  carbamic  acid  are 
exactly  analogous  to  those  of  the  amides  in  general : 

1.  By  the  action  of  ammonia  upon  ethyl  carbonate  : 

CO(OC2H,)2  +  2NH3  =  CO(NH2)2  +  2C2H,.OH. 
CO(OC2H,)2  +   NH3  =  CO(OCA)NH,  +  C,H,OH. 

2.  By  the  abstraction  of  the  elements  of  water  from  car- 
bonate or  carbamate  of  ammonia.  Dry  carbon  dioxide  and 
ammonia  combine  together  directly  to  ammonium  carbamate,  the 


270  XIII.  DERIVATIVES  OF  CARBONIC  ACID. 


so-called  anhydrous  carbonate  of  ammonia,  C0(NH2).0H,  NH3, 
which  goes  into  urea  when  heated  to  135°,  or  when  exposed 
to  the  action  of  an  alternating  current  of  electricity,  thus  : 

CO(NH2).OH,NH3  =  CO(NH2)2  +  H2O. 

3.  By  the  action  of  ammonia  upon  carbon  oxy-chloride  : 

COCI2  +  4NH3  =  CO(NH2)2  +  2NH4CI. 
CO(OC2H5)Cl  +  2NH3  =  CO(OC2H5)NH2  +  NH^Cl. 

Carbamic  acid,  C0(NH2)0H.  Carbamate  of  ammonia, 
which  forms  a  white  mass,  dissociates  at  60°  into  2NH3  +  CO2. 
Its  aqueous  solution  does  not  precipitate  a  solution  of  chloride 
of  calcium  at  the  ordinary  temperature,  since  calcium  car- 
bamate is  soluble  in  water,  but,  if  it  is  heated,  saponification 
into  CO2  and  NH3  ensues  and  calcium  carbonate  is  thrown 
down. 

Urethane,  CO{NH2)(OC2H5),  is  the  ethyl  ether  of  carbamic 
acid.  It  is  formed  according  to  method  3,  and  also  by  the 
direct  union  of  cyanic  acid  with  alcohol.  Large  plates,  easily 
soluble  in  water,  etc.  M.  Pt.  4:7°-50°,  Boils  unchanged  and 
acts  as  a  soporific. 

Analogous  Methyl-  etc.  ethers  of  carbamic  acid  are  also  known. 
They  are  all  readily  saponified  by  alkalies  into  the  alcohol,  CO2  and 
NH3,  and  go  into  urea  when  heated  with  ammonia. 

Carhamic  chloride,  CO^^  ^  is  obtained  by  the  action  of  COClg  upon 

NH4CI  at  400°.  It  forms  long,  compact,  colourless  needles  of  pungent 
odour.  M.  Pt.  50°,  B.  Pt.  61-62°.  It  reacts  violently  with  water, 
ammes,  etc.,  and  serves  for  the  synthesis  of  organic  acids  (see 
these).  Among  its  derivatives  is  e.g.  Di-methyl- carbamic  chloride, 
C0[N(CH3),]C1. 

In  the  same  way  alkylated  carbamic  acids,  CO(NHR)OH,  which  are 
only  stable  as  ethers,  have  been  prepared,  e.g,  Ethyl-carhamic  ether, 
ethyl-urethane,  COlNH.CgHsjtOCaHs),  a  liquid,  B.  Pt.  175°,  which  is 
formed  e.g.  by  the  direct  combination  of  cyanic  ether  with  alcohol  at 
100°. 

Urea,  carbamide,  CO(NH2)2.  Was  first  found  in  urine  in 
1773.  Is  contained  in  the  urine  of  mammals,  birds  and  some 
reptiles,  and  also  in  other  animal  fluids.  A  grown  man  pro- 
duces about  30  grm.  daily.    Urea  is  the  final  decomposition 


UREA. 


271 


product  from  the  oxidation  of  the  nitrogenous  compounds  in 
the  organism. 

Formation.  From  ethyl  carbonate,  carbamic  acid  and 
phosgene,  as  given  above,  and  synthetically  by  the  molecular 
transformation  of  ammonium  cyanate,  by  warming  its  aqueous 
solution  or  allowing  it  to  stand,  {JFohler,  1828;  see  pp.  1 
and  258)  ; 

CN.OH,  NH3  =  CO(NH2)2. 

It  is  further  formed  from  cyanamide  and  water  : 

CN— NH2  +  H2O  =  CO(NH2)2 ; 

by  the  partial  saponification  of  guanidine  (p.  278)  : 

C(NH)(NH2)2  +  H2O  =  CO(NH2)2  +  NH3 ; 

by  heating  oxamide  with  mercuric  oxide,  by  the  breaking  up  of  creatine, 
by  means  of  alkali,  and  by  the  oxidation  of  uric  acid,  etc.  etc. 

Preparation.  1.  By  evaporating  urine,  adding  nitric  acid, 
and  decomposing  the  separated  and  purified  nitrate  of  urea  by 
barium  carbonate.  2.  By  mixing  a  solution  of  potassium 
cyanate  (from  the  ferrocyanide),  with  ammonium  sulphate 
and  evaporating  : 

2CN0K  +  (NH4)2S04  =  CO(NH2)2  +  K^SO^. 

It  crystallizes  in  long  rhombic  prisms  or  needles  of  a  cooling 
taste,  which  are  very  readily  soluble  in  water,  readily  also  in 
alcohol,  but  not  in  ether.  M.  Pt.  132^  When  strongly 
heated  it  yields  ammonia,  cyanuric  acid,  biuret  and  ammelide. 
As  an  amide  it  is  readily  saponified  by  boiling  with  alkalies 
or  acids,  or  by  superheating  with  water  : 

CO(NH2)2  +  H2O  =  CO2  +  2NH3. 

Nitrous  acid  reacts  with  it  to  produce  carbon  dioxide, 
nitrogen  and  water  : 

CO(NH2)2  +  2NO2H  =  CO2  +  2N2  +  3H2O. 

Sodium  hypochlorite  and  hypobromite  act  in  a  similar 
manner,  (Bavj/,  Kriop).  Hufner^s  method  of  estimating  urea 
quantitatively  depends  upon  the  measurement  of  the  nitrogen 
thus  obtained,  (J.  pr.  Ch.  [2]  3,  1).    When  warmed  with 


272 


XIII.  DERIVATIVES  OF  CARBONIC  ACID. 


alcoholic  potash  to  100°,  urea  is  converted  into  cyanate  of 
potassium  and  ammonia.  The  basic  character  of  ammonia  is 
greatly  weakened  in  urea  by  the  influence  of  the  negative 
carbonyl. 

Among  the  salts  of  urea  with  acids  may  be  mentioned  Urea  nitrate, 
CON.2H4,  HNO3,  which  crystallizes  in  glancing  white  plates,  easily 
soluble  in  water  but  only  slightly  in  nitric  acid ;  also  the  chloride, 
oxalate  and  phosphate.  But  like  acetamide  urea  also  forms  salts  with 
bases,  especially  with  mercuric  oxide,  e.g.  CON2H4  +  2HgO  ;  finally  it 
yields  crystalline  compounds  with  salts,  e.g.  Urea  sodium  chloride, 
CON2H4  +  NaCl  +  HgO  (glancing  prisms),  and  Urea  silver  nitrate, 
CON2H4  +  AgNOg  (rhombic  prisms).  The  precipitate  which  is  ob- 
tained on  adding  mercuric  nitrate  to  a  neutral  aqueous  solution  of  urea 
has  the  formula  2CON2H4  +  Hg(N03)2  +  3HgO  ;  upon  its  formation 
depends  Liebig^s  method  for  titrating  urea.  (See  the  memoirs  of 
Pfluger  and  Bohland  on  the  subject,  e.g.  Pfli'iger^  Arch.  f.  Phys.  38, 
575). 

Isomeric  with  urea  is  the  amid-oxime  Isuret,  CH(NH)(NH.OH), 
which  results  from  HON  and  NHgOH  ;  it  crystallizes  in  prisms. 

Alkylated  ureas  are  obtained  by  the  exchange  of  the 
amido-hydrogen  atoms  for  1,  2,  3,  or  4  alcohol  radicles. 

They  are  produced  by  WdJiler^s  method  of  synthetizing  urea,  viz.  by 
the  combination  of  cyanic  acid  with  amines,  or  of  cyanic  ethers  with 
ammonia  or  amines,  thus  : 

CO.NC2H5  +  NH2.C2n5  =  CO(NH.C2H5)2. 

Also  from  amines  and  carbon  oxy-chloride.  As  examples  may  be  men- 
tioned : 

Methyl  urea,  00<^g2^jj^  ;  a-Di-ethyl  urea,  CO<^g-^2H5. 
Ethyl  urea,  C0<^^2^^^^  .     /3-Di-ethyl  urea,  C0<^J^2  jj^^^. 

They  are  in  part  very  similar  to  urea,  in  part  however  liquid  and 
volatile  without  decomposition.  Their  constitution  follows  very  simply 
from  the  nature  of  the  products  which  result  on  their  saponification  ; 
thus,  a-di-ethyl  urea  breaks  up  into  CO2  and  2  mols.  NHg.CgHg,  and 
the  /3-compound  into  CO2,  NH3  and  NH(C2H5)2,  in  accordance  with  the 
law  enunciated  on  p.  101,  that  alcoholic  radicles  which  are  directly 
bound  to  nitrogen  are  not  separated  from  it  by  saponifying  agents. 

For  Hydrazine  derivatives  of  urea,  see  p.  118. 

Acid  derivatives.  By  the  entrance  of  acid  radicles  into 
urea,  its  acid  derivatives  or  "Ureides"  result.    These  are 


DERIVATIVES  OF  UREA. 


273 


formed  by  the  action  of  acid  chlorides  or  anhydrides  upon 
urea,  or  by  the  action  of  phosphorus  oxy-chloride,  POCI3, 
upon  a  mixture  of  the  latter  with  the  acid.  They  correspond 
in  their  properties  to  di-acetamide  (p.  180).  To  this  class 
belong  Acetyl  urea,  CON2H3(C2H30),  and  Allophanic  acid, 
CO(NH2)(NH.C02H).  Divalent  monobasic  acids  also  form 
ureides,  not  only  in  virtue  of  their  alcoholic  nature,  but  as 
alcohol  and  acid  at  the  same  time,  thus  : 

Hydantoic  acid,  C0<^H.^3jj^_^.q^jj^  CH-CH3 

TT  J    4.  nr,  /NH.CO  Lactyl  urea,  C0<  | 

Hydantoin,        ^'^<jjjj  \nH.CO. 

Hydantoin  or-  glycolyl  urea,  C3H4N2O2  (needles,  neutral),  and 
Hydantoic  acid  or  glycoluric  acid,  03HgN203  (prisms),  are  derivatives  of 
glycollic  acid  ;  the  former  goes,  on  saponification,  into  hydantoic  acid, 
which  in  its  turn  is  broken  up  into  CO2,  N'Hg  and  glycocoll.  They  are 
obtained  from  certain  uric  acid  derivatives  [t.g.  allantoin)  by  the 
action  of  hydriodic  acid,  and  also  synthetically,  for  instanoe,  hydan- 
toic acid  from  glycocoll  and  cyanic  acid.  A  Methyl- hydantoin, 
C3H3(CH3)N202,  results  from  the  gentle  saponification  of  creatinine 
(p.  278),  NH  being  here  replaced  by  O. 

Methyl- uracyl,  CO<^-^jj  qq    ^^^CH,  is  a  ureide  resulting  from 

the  action  of  aceto-acetic  ether  upon  urea. 

For  ureides  of  dibasic  acids,  see  the  uric  acid  group,  p.  279. 


Biuret,  NH<CcO— NH^'  ~  C2H5N3O2,  is  obtained  by  heating  urea 
to  160° : 

2NH2.CO.NH2  =  NH3  +  NH(CO.NH2)2. 
It  crystallizes  in  white  needles  (  +  H2O),  readily  soluble  in  water  and 
alcohol.  The  alkaline  solution  gives  a  beautiful  violet-red  colouration 
on  the  addition  of  a  little  cupric  sulphate, — the  "  biuret  reaction." 
Biuret  also  results  from  the  action  of  ammonia  upon  the  Allophanic 
ethers,  crystalline  compounds  sparingly  soluble  in  water,  which  are 
prepared  from  urea  and  chloro- carbonic  ethers,  thus  : 

CO(NH2)2  +  CI.CO2C2H5  =  CO(NH2)(NH.C02C2H5)  +  HCl. 

Allophanic  acid  itself  is  not  known  in  the  free  state,  as  it 
immediately  breaks  up  into  urea  and  carbon  dioxide.  Biuret  may  be 
regarded  as  its  amide. 

(606)  •  S 


274 


XIII.  DERIVATIVES  OF  CARBONIC  ACID. 


Carbonyl  di-urea,  CO(NH.CO.NH2)2.  From  carbon  oxy-chloride 
and  urea  ;  prisms. 

D.  Sulphur  Derivatives  of  Carbonic  Acid. 

To  most  of  the  carbonic  acid  derivatives  which  have  been 
described,  there  exist  analogous  compounds  in  which  the 
oxygen  is  wholly  or  partially  replaced  by  sulphur.  Many  of 
these  again  are  unstable  in  the  free  state,  from  the  fact  of 
their  being  too  readily  saponifiable  to  COg,  COS  or  CSg,  but 
they  are  known  as  salts  or  at  least  as  ethers.  The  latter  are 
often  not  real  ethers,  in  so  far  that  those  which  contain  an 
alcoholic  radicle  linked  to  sulphur  do  not  yield  the  correspond- 
ing alcohols  on  saponification  (which  is  always  easy),  but 
mercaptans,  in  accordance  with  the  intimate  character  of  this 
linking. 

Among  these  ethers  there  exist  numerous  isomers  which 
cannot  be  described  in  detail  here.  Thus  we  are  acquainted 
with  two  varieties  of  mono-  and  of  dithio-carbonic  ethers, 
and  with  isomers  of  thio-  and  dithio-carbamic  ethers,  as  also 
of  the  alkylated  thio-ureas  (imido-carbamic  acid  derivatives). 
Of  the  acids  which  form  the  basis  of  these,  only  one  form  of 
each  is  known,  as  in  the  case  of  the  cyanogen  compounds ; 
the  remarks  already  made  with  respect  to  the  constitution  of 
the  latter  (p.  265,  F.)  apply  here  also. 

The  following  summary  gives  the  substances  (part  of  them 
being  only  known  as  derivatives)  wh  ch  form  the  basis  of 
these  compounds  : 

Tri-thiocarbonic  acid,  CS(SH)2 
Carbonyl  di-thio-acid,  COg-^ 
SH 

Di-thiocarbonic  acid,  ^^QH 
TCarbonylmono-thio-acidCOQg 
§  I^Mono-thiocarbonic  acid,  CSq^ 


■VTTT 

Thiocarbamic  chloride,  CS^j  ■ 


[3^^  rDi-thiocarbamic  acid,  CJS^^^ 
C(NH)|| 


Imido-carbo-di-  \ 
O  I    thio-acid,  j 


/  Carbamine  mono-thio-  ^  p,^NHo 

acid,  f^^SH. 
Mono-thiocarbamic  \  ^^NHg 

acid,  /  ^^OH 

Imido-carbo-        \  p.^v^TrxSH 
mono-thio-acid,  /  ^^^^"^^OH 

^  I  Thio-carbamide,  ^^NH" 
Imido-carbamine  ^ 


o 
o 


[lido-carbamine  1  /-</tvt-lt\^H 
thio-acid,        /  ^(^^^SH 
See  note.  p.  xxiii. 


DERIVATIVES  OF  THIO-CARBONIC  ACID. 


275 


The  above  table  shows  that  these  compounds  are  of  three 
kinds.  The  first  contain  the  group  =C=S,  and  are  called 
"  thiocarbonic "  and  thiocarbamic "  compounds;  the  second 
contain  the  group  =0=0,  and  are  termed  "  carbonyl "  and 
"  carbamine  "  compounds  ;  while  the  third,  which  contain  the 
group  =0=NH,  are  the  "  imido-carbo "  and  the  "  imido- 
carbamic^'  compounds. 

The  constitution  is  proved  experimentally  by  the  decomposition  pro- 
ducts obtained  by  the  saponification  of  the  isomeric  compounds.  Thus 
methyl  thio-carbamide  or  methyl  thio-urea,  CS(NH2)(NH.CH3)  (white 
crystals),  breaks  up  into  COg,  SH2,  NHg  and  methylamine,  while  the 
isomeric  imido-carbamic  thio-acid  methyl  ether  or  imido-carbamine- 
thio-methyl,"  C(NH)(NH2)(S.CH3),  is  decomposed  into  COg,  2NH3  and 
methyl  mercaptan,  or — when  in  the  free  state — into  methyl  mercaptan 
and  cyanamide. 

Thio-phosgene,  thiocarbonyl  chloride,  OSOI2.  When  chlorine 
is  allowed  to  act  upon  carbon  bisulphide,  there  is  first  formed 
the  compound  OOI3SOI,  which  is  converted  into  thio-phosgene 
by  SnOlg.  Thio-phosgene  is  a  red  mobile  strongly  fuming 
liquid  of  sweetish  taste,  which  attacks  the  mucous  membrane ; 
B.  Pt.  68-74°.  In  its  chemical  behaviour  it  closely  resembles 
phosgene,  but  is  much  more  stable  towards  water  than  the 
latter,  being  only  slowly  decomposed  even  by  hot  water.  It 
forms  ammonium  sulphocyanide — (not  thio-urea) — with 
ammonia.    (Of  B.  20,  2376 ;  21,  337.) 

Thiocarbonic  acids.  Tri-thiocarbonic  acid  is  made  up  of 
the  constituents  OSg  +  HgS,  so  that  carbon  bisulphide  is  its 
thio-anhydride,  while  the  di-thiocarbonic  acids  contain  the 
elements  of  OSg  +  HgO  or  of  OOS  +  HgS,  and  the  mono- 
acids  those  of  OOS  +  H2O  or  of  OOg  +  R^S.  We  find 
accordingly  that  OSg  combines  with  Na^S  to  OS3Na2,  with 
KSO2H5  to  OS(S02H5)SK,  with  KOO2H5  (ie.  an  alcoholic 
solution  of  potash)  to  OS(002ll5)SK,  potassium  xanthate. 
In  a  similar  manner  OOS  and  OSOI2  combine  with  mercaptides 
and  alcoholates. 

Tri-thiocarbonic  acid,  sulphocarhonic  acid,  CSoHg,  is  a  brown  easily 
decomposable  oil,  insoluble  in  water,  and  its  ethyl  ether,  CSgtCgllgja,  a 
liquid  boiling  at  240°. 


276  XIII.  DERIVATIVES  OF  CARBONIC  ACID. 


Potassium  Xanthate,  CS(OC2H5)SK,  (Zeise),  whose  prepara- 
tion has  been  given  above.,  crystallizes  in  beautiful  colourless 
needles,  very  readily  soluble  in  water,  less  so  in  alcohol. 
A  solution  of  cupric  sulphate  throws  down  cupric  xanthate  as 
a  yellow  unstable  precipitate,  hence  the  name.  It  is  employed 
as  an  antidote  for  Phylloxera  and  also  in  indigo  printing. 

With  ethyl  chloride,  C2HgCl,  there  is  formed  the  neutral  ether, 
CS(OC2Hg)(SC2H5).  The  free  Xanthic  acid,  or  ethoxy-di-thiocarhonic 
acid,  CS(OC2H5)SH,  is  an  oil  insoluble  in  water  which  decomposes  at 
so  low  a  temperature  as  25°  into  carbon  bisulphide  and  alcohol. 

Thio-carbamic  acids.  Di-thiocarbamic  acid,  CS(NH2)SH, 
is  formed  as  ammonia  salt  by  the  combination  of  CSg  and  NH3 
in  alcoholic  solution,  (see  p.  261)  : 

CS2  +  2NH3  =  CS(NH2)SH,  NH3. 

The  free  acid  is  a  reddish  oil  which  easily  decomposes  into 
thiocyanic  acid  and  sulphuretted  hydrogen  : 

CS(NH,)SH  -  CSNH  +  SHg. 

Carbon  bisulphide  combines  in  an  analogous  manner  with  primary 
amines  to  form  the  aminic  salts  of  alkylated  di-thiocarbamic 
acids ;  thus  ethylamine  yields  ethylamine  ethyl- di-thiocarbamate, 
CS(NH.C2H5)SH,  NH2C2H5.  When  such  salts  are  heated  above  100°, 
H2S  is  evolved  and  a  di-alkyl-thio-urea  left  behind,  e.g.  Diethyl-thio-urea, 
CS(NHC2H5).2 ;  when  HgCl2  or  Ag^03  is  added  to  their  solutions,  the 
Hg  or  Ag  salts  of  the  acids  are  precipitated,  and  these  decompose  on 
boiling  with  water  into  HgS  or  Ag2S  and  the  corresponding  mustard 
oil,  (cf.  p.  262)  : 

2CS(NHC2H5).SAg  -  2CSNC2H5  f  AggS  +  H^S. 

Secondary  amines  also  give  rise  to  alkylated  di-thiocarbamic  acids, 
but  the  latter  do  not  yield  mustard  oils,  (p.  114). 

Di-thio-uretliane,  CS(NH2)(S.C2Hg),  is  the  ethyl  ether  of  di-thiocar- 
bamic acid.  As  Thio-urethane  is  designated  the  ether  CO(NH2)(S.C2H5), 
and  as  Xanthamide  or  ethyl-thio-carbamide  its  isomer  CS(NH2)(OC2Hg). 
Methyl  xanthamide  is  thus  CS(]SrH.CH3)(O.C2H5),  and  so  on. 

Thiocarbamide,  thio-urea,  sulpho-urea,  CS(NH2)2,  {Reynolds), 
is  the  analogue  of  urea,  and  its  modes  of  formation  are  exactly 
analogous  to  those  of  the  latter.  Thus  it  is  formed  from 
ammonium  thiocyanate  just  as  urea  is  from  the  (iso)cyanate  : 

CSNH,  NH3  =  CS(NH2)2. 


THIO-UREA;  GUANIDINE. 


277 


To  effect  this  molecular  transformation  a  temperature  of  1 30' 
is  required,  and  it  is  only  partial,  since  thiocarbamide  goes 
b^ick  to  a  considerable  extent  into  ammonium  thiocyanate  on 
being  fused,  (see  p.  261).  It  results  further  by  the  direct 
combination  of  sulphuretted  hydrogen  with  cyanamide  : 

CN.NH2  +  SH2  =  CS(NH2)2. 
Thiocarbamide  crystallizes  in  rhombic  six-sided  prisms,  or — 
if  not  quite  pure — in  long  silky  needles,  readily  soluble  in 
water  and  alcohol.  M.  Pt.  171°.  -  It  is  easily  saponified  to 
CO2,  HgS  and  2NH3.  HgO  abstracts  H^S  from  it,  with 
formation  of  cyanamide.  As  a  weak  base  it  forms  salts  with 
acids,  but  at  the  same  time  it  yields  salts  with  HgO  and 
similar  bases ;  it  also  combines  with  salts,  such  as  AgCl, 
PtCl^,  etc.  When  heated  with  alcoholic  potash  to  100°,  it  is 
reconverted  into  (the  potassium  salt  of)  thiocyanic  acid  and 
ammonia.  Methyl  iodide,  CH3I,  reacts  with  it  to  produce 
imido-carbamine-thio-me  th  yl,  C(NH)  (NH2)  (S.  CH3),  already 
mentioned  at  p.  275,  {Bernthsen  and  Klinger), 

A  large  number  of  alkylated  derivatives  are  obtained  from  thio-urea 
and  also  from  the  isomeric  hypothetical  imido-carbamine-thio-acid, 
C(NH)(NH2).SH.  The  Alkyl  thio-ureas  are  in  part  broken  up  by 
hydrochloric  or  phosphoric  acid  into  amine  and  iso-thiocyanate  (p.  263), 
and  are  in  part  desulphurized  by  HgO  with  formation  of  alkyl  ureas  or 
alkyl  cyanamides.  When  desulphurization  takes  place  in  presence  of 
ammonia,  alkylated  guanidines  result. 

Acid  derivatives  of  thio-urea,  e.g.  Acetyl- thio-urea,  are  also  known. 
To  this  class  belongs,  among  other  compounds,  Thio-hydantoin,  which 
is  however  only  to  some  extent  analogous  to  the  hydantoin  described  on 
p.  273,  since  it  is  a  derivative  of  the  imido-carbamine-thio-acid  and 
yields  thio-glycollic  acid  when  decomposed,  these  reactions  agreeing 
NH— CO 

with  the  formula  C(NH)<^_g  CH2*  prepared  synthetically 

and  crystallizes  in  long  needles. 

E.  Amidines  of  Carbonic  Acid. 

Guanidine,  CH.Ng,  =  C(NH)(NH2)2,  {Strecker,  1861).  This 
compound  may  also  be  termed  imido-urea  or  imido-carbamide, 
thus  :  0=C-=(NH2)2,  urea ;  (NH)=C=(NH2)2,  guanidine. 


278 


XIII.  DERIVATIVES  OF  CARBONIC  ACID. 


Formation.  By  the  oxidation  of  guanine  (p.  284),  also  by 
heating  cyanamide  with  ammonium  iodide,  and  therefore  from 
cyanogen  iodide  and  ammonia  : 

CN.NH2  +  NH4I  =  CN3H,,  HI. 

Preparation.  By  heating  thio-urea  with  ammonium  thio- 
cyanate  to  180-190°  and  therefore  from  the  thiocyanate  alone 
at  this  temperature,  (Volhard) : 

CS(NH2)2  +  NH3.CNSH  =  C(NH)(NH2)2,  CNSH  +  H^S. 

Guanidine  is  a  very  strong  crystalline  base,  readily  soluble 
in  water  and  alcohol,  which  deliquesces  in  the  air  and  absorbs 
carbonic  acid,  and  combines  with  one  equivalent  of  acid  to 
form  salts.  G-uanidine  carbonate,  (01^3115)2,  H2CO3,  crystal- 
lizes beautifully  in  quadratic  prisms.  Gruanidine  is  readily 
saponifiable,  at  first  to  urea  and  ammonia,  and  finally  to 
ammonia  and  carbon  dioxide. 

Numerous  alkylated  guanidiues  have  been  prepared  by  the  action  of 
ammonia,  etc. ,  upon  alkyl  thio-ureas,  and  by  the  combination  of  cyana- 
mide with  amines,  etc.  They  break  up  on  being  heated  with  H2S  or 
CS2,  with  reproduction  of  thio-ureas  and  amines,  or  of  thio-  or  iso- 
thiocyanate,  (see  Amidines,  p.  185). 

By  the  direct  combination  of  cyanamide  with  glycocoU  there  is 
NH 

formed  Glycocy amine,  C(^H)]s^jj!_c;jj  qq  jj>  which  gives  up  water 

with  formation  of  Glycocyamidine,  C(NH)  •     .    If,  instead  of 

JN  xi — 

glycocoll,  its  methyl  derivative  sar cosine  is  used,  one  obtains  in  an 
analogous  manner  creatine  and  creatinine,  ( Volhard)  : 

Creatine.  Creatinine. 

Creatine,  C4H9N3O2,  (Chevreul),  is  present  in  the  juice  of 
muscle  and  is  prepared  from  extract  of  meat,  (Liehig).  It 
crystallizes  in  neutral  glancing  prisms  ( +  HgO)  of  a  bitter  taste, 
moderately  soluble  in  hot  w^ater  but  only  slightly  in  alcohol. 
When  heated  with  acids  it  loses  water  and  goes  into 

Creatinine,  C4H7N3O,  which  is  an  invariable  constituent  of 
urine  and  which  forms  a  characteristic  double  salt  with  zinc 
chloride,  2C4H^N30  +  ZnClg.    It  is  a  strong  base  and  much 


URIC  ACID  GROUP. 


279 


more  readily  soluble  in  water  and  alcohol  than  creatine,  into 
which  it  can  be  reconverted  by  taking  up  water.  When  mildly 
saponified,  creatinine  yields  ammonia  and  methyl-hydantoi'n, 
while  creatine  gives  urea  and  sarcosine. 


F.  Uric  Acid  Group. 

Just  as  the  dibasic  acids  oxalic,  malonic,  tartronic  and 
mesoxalic  yield  amides  with  ammonia,  so  can  they  react 
with  the  ammonia  derivative,  urea,  to  form  compounds  of  an 
amidic  nature.  In  such  reactions  either  two  molecules  of  water 
separate,  so  that  no  more  carboxyl  remains  in  the  compound, 
or  only  one  molecule  is  eliminated  and  a  carboxyl  group 
remains.  In  the  former  case  the  so-called  ^*ureides"  result, 
and  in  the  latter  the  so-called  "  ureide-acids,"  e,g.,  from  oxalic 
acid,  parabanic  and  oxaluric  acids : 

CO.OH  ^NH.CO  ^jj^ 

CO.OH  ^°\nH.CO  ^^^NHfcO.CO^H 

Oxalic  acid.     Ureide  (parabanic  acid).    Ureide-acid  (oxaluric  acid). 

In  an  analogous  manner  the  ureide  barbituric  acid, 
O4H4N2O3,  is  derived  from  malonic  acid,  the  ureide  dialuric 
acid,  C4H4N2O4,  from  tartronic  acid,  and  the  ureide  alloxan, 
C4H2N2O4,  and  ureide-acid  alloxanic  acid,  C^H^NgOg,  from  mes- 
oxalic acid. 

These  are  solid  and,  for  the  most  part,  beautifully  crystalliz- 
ing compounds  of  a  normal  amidic  character,  and  therefore 
easily  broken  up  backwards  by  saponification  into  urea  (or 
CO2  and  NH3)  and  the  respective  acid.  The  ureide-acids  may 
be  regarded  as  half-saponified  ureides,  resulting  in  fact  from 
the  latter  in  this  manner. 

Analogous  compounds  are  also  derived  from  the  aldehydic- 
or  alcoholic-acids,  glyoxalic  acid,  CH(0H)2 — COgH,  and  gly- 
coUic  acid,  CH2(0H) — CO2H  ;  from  the  former  allanturic  acid, 
C3H4N2O3,  and  from  the  latter  the  ureide  hydantoin  and  the 
ureide-acid  hydantoic  acid,  (see  p.  273).  They  show,  however, 
a  somewhat  different  behaviour  on  saponification.    In  addition 


280 


XIII.  DERIVATIVES  OF  CARBONIC  ACID. 


to  these  so-called  "  mono-ureides  "  there  exist  also  "  di-ureides/' 
^. 6.,  compounds  into  whose  composition  two  molecules  of  urea  have 
entered.  These  are  uric  acid,  C^H^N^Og,  and  its  near  relations 
xanthine,  theobromine,  C5H2(CH3)2N402,  caffeine, 

C5H(CH3)3N402,    hypoxanthine,    C^H^N^O,    and  guanine, 
;    further,   purpuric   acid,    CgHgN^Og,  alloxantin, 
CgH^N^O^,  allantoin,  0^11^^403,  and  other  compounds. 

Several  of  these  di-ureides  occur  in  nature.  Uric  acid  is 
contained  in  the  urine,  blood  and  muscle  juice  of  the  carnivora, 
in  gravel  and  chalk  stones,  in  guano,  and  in  the  excrementa  of 
serpents ;  xanthine  in  small  quantity  in  the  urine,  blood  and 
liver,  and  sometimes  in  gravel,  almost  always  together  with 
hypoxanthine;  guanine  in  guano;  and  carnine  in  extract  of 
meat.  Theobromine  is  present  in  the  cocoa  bean  (Theobroma 
Cacao),  and  caffeine  in  the  coffee  bean,  in  tea,  in  Paraguay  tea 
(Ilex  paraguayensis),  and  in  the  guarana  (the  fruit  of  Paullinia 
sorbilis),  etc. 

Many  of  these  compounds  are  nearly  related  to  one  another ;  thus  ' 
xanthme  and  hypoxanthine  are  formed  by  the  action  of  sodium  amalgam 
upon  uric  acid,  (taking  away  of  0),  xanthine  by  the  action  of  nitrous 
acid  upon  guanine,  (exchange  of  N  and  H  for  0),  theobromine  and 
caffeine  by  the  methylation  of  xanthine,  and  hypoxanthine  by  the 
action  of  nitric  acid  upon  carnine. 

Formation.  The  ureides  mentioned  above  or  other  diureides 
result,  frequently  together  with  urea,  by  the  oxidizing  de- 
composition (or  oxidation)  of  the  diureides  which  have  been 
enumerated. 

Thus  uric  acid  yields  allantoin  with  water  and  PbOg  and  either 
purpuric  acid,  alloxan,  alloxantin  or  parabanic  acid  with  nitric  acid, 
according  to  the  conditions,  while  caffeine  yields  dimethyl-alloxan 
and  methyl-urea  with  chlorine.  These  decomposition  products  also 
stand  in  an  intimate  relation  to  one  another,  e.g.,  alloxan  gives  alloxan- 
tin, dialuric  acid  and  barbituric  acid  on  reduction ;  hydantoin  results 
e.g.  from  the  oxidation  of  alloxanic  acid  and  is  itself  oxidized  to 
allanturic  acid  ;  while  dialuric  acid  and  alloxan  combine  to  alloxantin 
with  elimination  of  water,  etc.,  etc. 

Some  of  these  ureides  have  also  been  prepared  synthetically  from 
urea  and  the  requisite  acid,  phosphorus  oxy-chloride  having  proved 
itself  to  be  particularly  useful  as  a  dehydrating  agent  in  such  cases ; 
in  this  way  parabanic  acid  has  been  obtained  from  oxalic,  and  barbituric 


PARABANIO  ACID. 


281 


acid  from  malonic.  Uric  acid  may  be  syntlietized  by  heating  glycocoll 
Avith  urea,  {Horhaczeivski,  B.  15,  2678),  and  also  by  heating  trichloro- 
lactic  or  monochlor-acetic  acid  with  urea,  (B.  20,  R.  472,  R.  723),  and 
therefore  also  xanthine,  theobromine  and  caffeine  indirectly. 

The  constitution  of  the  simpler  ureides  and  ureide-acids  follows 
directly  from  their  decomposition  products,  syntheses  and 
relations  to  one  another,  while  considerations  of  a  more  com- 
plex nature  have  led  to  the  constitution  of  uric  acid,  (Medicus), 
and  of  xanthine  and  its  more  nearly  allied  compounds,  {E. 
Fischer,  A.  215,  253) : 

/  >C0;  /  (1)      .  >C0 

C0(  C— NH^  CO<C         C— NH-^ 

\  .  \  ..  (3) 

NH— CO  NH— CH 

Uric  acid.  Xanthine. 

Guanine  is  imido-xanthine  (0  being  replaced  by  NH) ;  theobromine 
and  caffeine  are  di-  and  trimethyl-xanthines  (the  H  atoms  1  and  3,  or 
1,  2  and  3  being  replaced  by  CHg).  From  this  it  follows  that  uric  acid 
is  the  di-ureide  of  the  unknown  compound,  C(0H).2=C(0H) — COgH, 
or  of  the  hydrate  of  tartronic  acid,  C(0H)3— CH(OH)— COOH. 

Most  of  the  ureides  and  di-ureides  have  the  character  of 
more  or  less  strong  acids. 

Since  this  acid  character  is  not  to  be  explained,  as  in  the  case  of  the 
ureide-acids,  by  the  presence  of  carboxyl,  one  must  assume  that  it  depends 
upon  reasons  similar  to  those  which  apply  in  the  case  of  cyanic  acid  and 
of  succinimide,  viz.,  that  the  replaceable  hydrogen  atoms  are  imido- 
hydrogen  atoms  whose  chemical  nature  is  determined  by  the  surround- 
ing carbonyl  groups.  This  explains,  for  instance,  why  parabanic  acid 
is  a  strong  dibasic  acid. 

Only  a  few  of  the  more  important  among  these  compounds 
can  be  discussed  here.  (Of  Liehig  and  Wohler,  A.  26,  241 ; 
Baeyer,  A.  127,  1,  199 ;  130,  129,  etc.) 

/NH.CO  . 

Parabanic  acid,  CO^        i   ,  is  prepared  by  the  action  of 
\NH.CO 

nitric  upon  uric  acid,  and  crystallizes  in  needles  or  prisms  soluble 
in  water  and  alcohol.    The  salts,  e.g.,  CoHKNgOg,  CgAg^NgOg, 
are  unstable,  being  converted  by  water  into  salts  of  the  mono- 
NH 

basic  Oxaluric  acid,  C0<^-^ jj^qq       jj,  which  crystallize  well. 


282  XIII.  DERIVATIVES  OF  CARBONIC  ACID. 


A  Methyl-paratoanic  acid,  C0<^  i   ,  and  a  Di-methyl-para- 

NH   CO 

N(CH3)— CO 

banic  acid,  the  so-called    Cholestrophane, "  CO<r^^  '  ^,  are  also 

^NtCHg)— CO 

known.  The  former  is  prepared  e.g.  by  the  action  of  nitric  upon 
methyl-uric  acid  and  crystallizes  in  prisms,  while  the  latter  is  obtained 
from  theine  with  nitric  acid,  chlorine  water,  etc.,  and  also  by  the 
methylation  of  parabanic  acid,  i.e.  from  the  Ag  salt  and  CH3I.  It 
crystallizes  in  plates  and  distils  without  decomposition. 

Barbituric  acid,  malonyl  urea^  C4H4N2O3,  is  a  dibasic  acid, 
crystallizing  in  large  colourless  prisms  ( +  2H2O).  It  is  the 
H-atoms  of  the  methylene  group,  CHg,  and  not  of  the  imido- 
group  which  are  replaceable,  since  dimethyl-malonyl-urea, 
which  can  be  prepared  from  the  silver  salt  and  methyl  iodide, 
does  not  yield  malonic  acid  when  boiled  with  alkalies,  but 
dimethyl-malonic  acid,  (CH3)2=C(C02H)2. 

Dialuric  acid,  tartromjl  urea,  C^H^NgO^.  Strong  dibasic 
acid.  Crystallizes  in  colourless  needles  or  prisms  which 
redden  in  the  air  and  go  into  alloxantin  upon  oxidation. 

Alloxan,  mesoxalyl  urea,  CO<^-|^jj  qq^CO.  Prepared 

from  uric  acid  and  cold  HNO3.  Large  colourless  glancing 
rhombic  prisms  ( +  4H2O),  strongly  acid  and  readily  soluble  in 
water.  Colours  the  skin  purple-red.  Ferrous  sulphate  pro- 
duces an  indigo  blue  colour  with  its  solution.  It  combines 
with  NaHSOg  and  readily  changes  into  alloxantin.  The 
corresponding  **ureide-acid,"  Alloxanic  acid,  C4H4N2O5,  which 
alloxan  yields  even  with  cold  alkali,  forms  a  radiating  crystalline 
mass  readily  soluble  in  water.  Methyl-  and  Dimethyl-alloxan 
are  also  known,  being  obtained  by  the  action  of  nitric  acid 
upon  methyl-uric  acid  and  caffeine  respectively. 

The  di-ureide  Alloxantin,  CgH^N^O^,  stands  mid-way  in 
composition  between  tartronyl-  and  mesoxalyl-urea,  by  the 
combination  of  which  it  is  formed. 

One  obtains  it  by  acting  on  alloxan  with  H2S  or  directly  from  uric 
acid  and  HNO3.  It  crystallizes  in  small  hard  prisms  (-f-SHoO),  which 
become  red  in  air  containing  ammonia,  their  solution  acquiring  a  deep 
blue  colour  on   the  addition  of  FeaCle  and  NH3.     The  tetra-methyl 


URIC  ACID. 


283 


derivative,  Amalic  acid,  Cy(CH3)4N407,  results  from  theine  and  chlorine 
water,  and  forms  colourless  crystals  which  redden  the  skin  and  whose 
solution  is  turned  violet-blue  by  alkali.  Both  these  compounds  yield, 
upon  oxidation,  first  alloxan  or  its  di-methyl  derivative,  and  then 
parabanic  or  dimethyl-parabanic  acid.  Thus  alloxantin  has  perhaps 
the  constitution  : 

C0<gizg8>C(0H)-0-CH<C0-NH>0. 

When  heated  with  ammonia  it  is  converted  into  Murexide, 
the  acid  ammonium  salt  of  Purpuric  acid,  CgH5N50g(  -i-  H^O), 

perhaps  CO<5JgZco>^(OH)-NH-CH<gg-^g>CO, 

which  is  formed  when  uric  acid  is  evaporated  with  dihite 
nitric  acid,  and  ammonia  added  to  the  residue ;  this  is  the 
"  murexide  test    for  uric  acid. 

Murexide  crystallizes  in  four-sided  tables  or  prisms  (-fHgO)  of  a 
golden-green  colour,  which  dissolve  to  a  purple-red  solution  in  water 
and  to  a  blue  one  in  potash.    The  free  acid  is  incapable  of  existence. 

Allantoin  is  a  di-ureide  of  glyoxylic  acid,  of  the  constitution 

NH-CH— NH  ^ 
C0<^  I  ^CO,  which  is  found  in  the  allantoic 

NH — CO  NHg 

liquid  of  the  cow,  the  urine  of  sucking  calves,  etc.  It  forms 
glancing  prisms  of  neutral  reaction,  yields  salts  with  alkalies, 
and  can  be  prepared  synthetically  from  its  components. 

Uric  acid,  C^H^N^Og,  {Scheele,  1776).  For  occurrence  and 
synthesis,  see  above.  Is  prepared  from  guano  and  the  excre- 
ment of  serpents  and  crystallizes  in  small  tables.  Almost 
insoluble  in  water  and  insoluble  in  alcohol  and  ether,  but  con- 
centrated sulphuric  acid  dissolves  it  without  decomposition, 
and  from  this  solution  it  is  thrown  down  unchanged  by  water. 
For  the  murexide  reaction,  see  above.  Uric  acid  is  a  weak 
dibasic  acid  ;  its  common  salts  are  the  primary  (i.e.,  hydrogen) 
ones,  e.g.  C5H3KN4O3,  a  powder  sparingly  soluble  in  water. 

When  the  two  lead  salts  are  treated  with  methyl  iodide,  Methyl-  and 
Dimethyl-uric  acid  are  obtained,  both  of  which  also  are  w^eak  dibasic 
acids,  since  they  still  contain  replaceable  imido-hydrogen  atoms. 

Uric  acid  yields  alloxan  and  urea  when  cautiously  oxidized, 
and  dimethyl-uric  acid  methyl-alloxan  and  methyl-urea,  a  de- 


284 


XIII.  DERIVATIVES  OF  CARBONIC  ACID. 


composition  which  is  readily  understood  from  the  above  consti- 
tutional formula,  thus  : 


G0(       C-Nir      H-O  +  H^O^CO^  co'^'nh^ 


Xanthine,  C5H4N4O2,  is  produced  from  guanine  and  nitrous  acid,  and 
from  uric  acid  and  sodium  amalgam.  It  is  a  white  amorphous  mass, 
and  is  at  the  same  time  base  and  acid  ;  thus  it  yields  e.g.  the  lead 
compound  CgH2PbN402,  which  is  converted  into  theobromine  by  methyl 
iodide. 

Hypoxanthine,  sarcine,  C5H4N4O.  Sparingly  soluble  in  water  and 
very  like  xanthine. 

Theobromine,  C^HgN^Og.  Crystalline  powder  of  bitter 
taste,  sparingly  soluble  in  water  and  alcohol.  Forms  salts 
both  as  base  and  as  acid.  The  silver  salt,  C^H.jrAgN402, 
yields  caffeine  when  treated  with  CH3I,  (Strecker,  Fischer). 

Caffeine  or  Theine,  CgH^oN^Og.  Crystallizes  ( -i-  HgO)  in 
beautiful  long  glancing  silky  needles  of  faintly  bitter  taste, 
which  are  sparingly  soluble  in  cold  water  and  alcohol,  and  can 
be  sublimed.  The  salts  are  readily  decomposed  by  water. 
Chlorine  breaks  it  up  into  dimethyl-alloxan  and  mono- 
methyl-urea,  a  reaction  easily  understood  from  the  constitu- 
tional formula  given  on  p.  281. 

Guanine,  C5H5N5O.  White  amorphous  powder  insoluble  in  water  but 
soluble  in  ammonia.  It  is  a  divalent  base,  but  also  forms  salts  with 
bases.  Yields  guanidine,  parabanic  acid  and  carbon  dioxide  with 
KCIO3  +  HCl.  Is  an  imide  of  xanthine,  containing  NH  instead  of 
O,  and  hence  nitrous  acid  converts  it  into  the  latter  compound. 

Adenine,  C5H5N5,  which  is  a  polymer  of  hydrocyanic  acid,  is  a  base 
which  results  from  the  decomposition  of  nuclein  (see  this) ;  it  has 
been  obtained  from  the  pancreatic  glands  of  oxen  and  from  tea  leaves. 
It  crystallizes  in  long  needles  and  is  converted  by  nitrous  acid  into 
hypoxanthine,  whose  imide  it  therefore  is. 

Carnine.    A  powder  rather  easily  soluble  in  hot  water. 


,NH-C-Na 


,NH-CO  NHg, 


THE  CARBOHYDRATES. 


285 


XIV.  CARBOHYDRATES. 

As  carbohydrates  are  designated  three  groups  of  compounds 
nearly  allied  to  one  another  and  which  are  very  widely  distri- 
buted in  nature,  viz.,  those  of  grape  sugar,  CgH^gOg,  of  cane 
sugar,  and  of  cellulose,  (CgHioOg)!,.    All  of  them 

contain  6  atoms  of  carbon  or  some  multiple  of  6,  and  hydrogen 
and  oxygen  in  the  same  proportion  in  which  these  elements 
are  present  in  water.  They  are  nearly  related  to  the  hexa- 
tomic  alcohols,  CgH^^Og,  from  which  they  are  respectively 
derived  by  the  abstraction  of      or  of  Hg  +  HgO. 

Most  of  the  carbohydrates  have  been  known  for  a  long  time.  Cane 
sugar  was  found  in  the  sugar  beet  by  Margrafin  1747,  and  dextrose  in 
honey  by  Glauber. 

The  transformation  of  starch  into  sugar  (p.  293)  was  first  observed 
by  Kirchoff  in  1811. 

A  characteristic  and  extremely  delicate  reaction  of  the  carbohydrates 
consists  in  their  giving  a  beautiful  deep  violet  colouration  with 
a-naphthol  and  concentrated  sulphuric  acid,  [Molisch,  B.  19,  R.  746). 

A.  The  Grape  Sugar  Group,  G^iP^. 

{Glucoses^  Gly coses.) 

The  glucoses  are  sweet  and  for  the  most  part  crj^stalline 
compounds  easily  soluble  in  water,  sparingly  soluble  in  abso- 
lute alcohol  and  insoluble  in  ether.  They  possess  the  character 
of  polyvalent — (pentavalent) — alcohols  and  closely  resemble 
mannite,  etc.,  but  differ  from  it  in  being  fermentable,  in 
having  strongly  reducing  properties,  and  in  their  behaviour 
towards  phenyl-hydrazine  (see  below).  Most  of  them  are 
optically  active. 

The  glucoses  result,  apart  from  their  formation  in  plants, 
from  the  carbohydrates  of  the  cane  sugar  and  starch  groups  by 
the  taking  up  of  water,  and  also  from  the  decomposition  of  the 
glucosides  by  dilute  acids.  Those  which  occur  in  nature  can- 
not yet  be  said  to  have  been  prepared  synthetically  with 
certainty,  but  glucoses  which  very  closely  resemble  them  have. 


286 


XIV.  CARBOHYDRATES. 


Butlerow  (A.  120,  295)  obtained  the  so-called  "  methylenitan  " 
by  the  action  of  lime  water  upon  paraformic  aldehyde  (tri-oxy- 
methylene,  p.  135),  and  0.  Loew  (J.  pr.  Ch.  [2]  33,  321)  prepared 
"formose"  from  formic  aldehyde  itself  in  a  similar  manner. 
Both  of  these,  especially  the  former,  are  sweet  amorphous 
mixtures  of  various  compounds,  possessing  reducing  powers 
and  containing  at  least  one  real  glucose.  Fischer  and  Tafel  (B. 
20,  2566)  then  succeeded  in  synthetizing  sugar  varieties  which 
they  termed  a-  and  ^-acrose  (see  below),  by  the  action  of  baryta 
water  upon  acrolein  bromide  or  glycerine  aldehyde,  but  it  is 
as  yet  impossible  to  state  absolutely  whether  or  not  these  are 
identical  with  natural  glucoses.  Lsevulose  and  mannose  result 
from  the  cautious  oxidation  of  mannite. 

Their  constitution  has  not  yet  been  determined  with  certainty. 
On  account  of  the  close  connection  of  dextrose,  laevulose  and 
galactose  with  the  hexatomic  alcohols,  one  must  regard  them 
as  the  first  oxidation  products  of  the  latter,  and  therefore 
assume  that  their  carbon  chain  is  normal  and  that  each  of  their 
hydroxyls  is  linked  to  a  different  carbon  atom.  They  may 
thus  be  either  aldehyde-alcohols  {Baeyer,  Fittig)^  or  ketone- 
alcohols  (F".  Meyer),  in  either  of  which  cases  their  reducing 
properties  are  easy  to  understand,  (see  acetol,  p.  221).  Dex- 
trose, Isevulose  and  galactose  unite  with  HON  to  cyanhydrins, 
which  are  converted  into  carboxylic  acids  of  the  formula 
CgH^30g(C02H)  upon  saponification.  The  constitution  of  the 
latter  speaks  in  favour  of  the  following  formulae,  (Kiliani, 
B.  18,  3066 ;  19,  767) : 

Dextrose  =  CH2(0H)— [CH(0H)]4— CHO ; 
Lsevulose  =  CH2(0H)— [CH(0H)]3-C0— CH2(0H). 

Behaviour.  1.  Fermentation.  Most  of  the  glucoses  are 
directly  fermentable.  With  the  exception  of  sorbin,  they 
ferment  with  yeast  (galactose  only  with  difficulty),  undergo 
the  lactic  or  butyric  fermentation  with  bacteria,  and  are  trans- 
formed under  certain  conditions  into  mucous  dextrine-like 
substances  by  the  "  mucous "  fermentation. 

2.  Grape  sugar  is  a  pentatomic  alcohol,  yielding  e,g,  a  di- 


GLUCOSES;  GRAPE  SUGAR. 


287 


and  a  tri- acetyl  compound,  a  tetra- acetyl  chlorhydrin, 
C^H^OCKO.C^H^O)^,  and  a  tetra-acetyl  nitrin,  C6H^O(O.N02) 
(O.CgHgO)^.    The  other  glucoses  show  a  similar  behaviour. 

3.  The  glucoses  form  alcoholates  (saccharates)  with  bases, 
especially  with  lime,  compounds  which  are  decomposed  by  CO2, 
and  which  become  brown  in  the  air  from  oxidation.  By  the 
further  action  of  lime,  saccharic  acids  are  produced.  Alkalies 
decompose  glucoses  with  production  of  a  brown  colour  and 
formation,  e.g.  of  lactic  acid. 

4.  Lsevulose  is  converted  into  mannite  by  sodium  amalgam, 
and  dextrose  also,  though  less  completely: 

lactose  is  similarly  transformed  into  dulcite. 

5.  The  glucoses  are  readily  oxidizable,  and  therefore  they 
reduce  an  ammoniacal  silver  solution  and  also  Fehling's 
solution  if  warmed  with  it.  The  oxidation  of  grape  sugar 
yields,  according  to  the  conditions,  gluconic,  saccharic,  tartaric 
or  oxalic  acid;  that  of  fruit  sugar,  glycollic,  erythritic  or 
racemic  acid,  etc.;  and  that  of  lactose,  galactonic  or  mucic  acid. 

6.  When  boiled  with  dilute  sulphuric  acid,  the  glucoses — especially 
Isevulose — are,  like  the  other  carbohydrates,  converted  into  laevulinic  acid. 
(Cf.  A.  243.) 

7.  With  phenyl-hydrazine,  CeHs  —  NH  —  NHo,  there  are  first 
produced,  with  elimination  of  water,  compounds  of  the  formula 
C6Hi205(N2HC6H5),  compounds  which  are  "hydrazones,"  and  the  for- 
mation of  which  demonstrates  the  aldehydic  or  ketonic  character  of  the 
glucoses.    When  the  action  is  allowed  to  go  further,  a  second  molecule 

of  phenyl-hydrazine  enters  the  compound,  or  rather  [  is  replaced 

— OH  ) 

by  rrNoHCeHs,  and  "osazones,"  C6Hio04(N2HC6H5)2,  result,  e.g.  phenyl- 
dextrosazone,  phenyl-acrosazone,  and  phenyl-lactosazone.  These  are 
yellow  crystalline  compounds  which  are  of  great  value  for  the  recogni- 
tion of  the  carbohydrates.  By  the  action  of  nascent  hydrogen  upon 
them,  the  phenyl-hydrazine  radicles  are  eliminated  down  to  one  amido- 
-  group,  the  glucosamines  result,  e.g.  iso-glucosamine,  CGHHO5NH2,  from 
phenyl-glucosazone ;  the  latter  may  then  in  their  turn  be  converted  into 
glucoses  by  nitrous  acid  [Fischer  and  Tafel,  B.  20,  2566).  The  con- 
ception of  the  osazones  has  also  been  extended  to  the  analogously  con- 
stituted derivatives  of  other  aldehyde-  and  ketone-alcohols,  e.g.  glyceric 
aldehyde. 


288 


CARBOHYDRATES. 


8.  When  heated,  the  glucoses  at  first  change  into  compounds  of  the 
nature  of  anhydrides  and  then  into  others  of  the  nature  of  caramel 
(p.  291),  and  finally  they  become  charred. 

9.  They  do  not  show  the  aldehydic  reaction  with  fuchsine  and 
sulphur  dioxide. 


Grape  sugar  or  Dextrose,  OgH^gOg  +  HgO,  occurs  along 
with  Isevulose  in  most  sweet  fruits,  also  in  diabetic  urine,  etc., 
etc. 

It  is  prepared  from  other  carbohydrates,  as  given  at  pp.  289 
and  292.  The  sugar  which  is  obtained  from  starch  and 
termed  starch  sugar  contains,  in  addition  to  dextrose, 
dextrine  and  unfermentable  substances.  It  crystallizes  from 
water  in  granulous  masses  made  up  of  six-sided  plates,  and 
from  methyl  alcohol  in  small  anhydrous  prisms.  M.  Pt.  146°. 
It  is  dextro-rotatory,  hence  the  name  ^'dextrose." 

A  freshly  prepared  solution  turns  the  plane  of  polarization  almost 
twice  as  much  as  one  which  has  been  kept  or  heated  to  boiling,  a 
phenomenon  which  is  known  as  bi-rotation."  For  the  estimation  of 
grape  sugar  by  means  of  Fehling''s  solution,  see  e.g,  J.  pr.  Ch.  [2]  21, 
254. 

Truit  sugar  or  LsBVulose,  G^-^^O^,  is  almost  invariably 
found  along  with  dextrose  in  the  juice  of  sweet  fruits  and  also, 
together  with  the  latter,  in  honey.  It  is  formed  along  with 
dextrose  by  the  inversion  of  cane  sugar,  and  together  with 
mannose  by  the  cautious  oxidation  of  mannite  by  nitric  acid, 
and  is  easily  prepared  by  heating  inulin  with  water  and  a 
little  acid.  It  crystallizes  with,  difficulty  in  needles  of  M.  Pt. 
95°,  being  usually  obtained  as  an  amorphous  gum,  and  turns 
the  plane  of  polarization  more  stronglj?-  to  the  left  than  dextrose 
does  to  the  right. 

Phenyl-glucosazone,  C6Hio04(N2HC6H5)2,  M.  Pt.  204°,  forms  difficultly 
soluble  needles,  (B.  17,  579).  It  results  from  the  action  of  phenyl- 
hydrazine  upon  either  dextrose  or  Isevulose.  When  reduced  it  goes  into 
iso-glucosamine,  which  is  converted  by  nitrous  acid  into  Isevulose.  By 
this  reaction  it  is  thus  possible  to  convert  dextrose  into  Isevulose. 

Galactose  or  Lactose,  CgH^gOg,  is  produced  along  with 


THE  CANE  SUGAR  GROUP. 


289 


dextrose  from  milk  sugar  and  dilute  acid.  Fine  needles,  M. 
Pt.  143°.  Dextro-rotatory. 

a-  and  |8.Acrose,  CqR^^Oq,  {Fischer  and  Tafel,  B.  20,  2566).  For 
synthesis,  see  p.  286.  a-Acrose  resembles  dextrose  so  closely  that  it  is 
possibly  only  a  physical  (optically  inactive)  modification  of  the  latter. 

Mannose,  CgHigOg.    See  above,  also  B.  21,  1805. 

Sorbin,  CgHigOe.  Present  in  the  juice  of  the  sorb  apple.  Large 
crystals. 

Inosite,  phaseo-mannite,  damhose,  CgHigOg  +  2H2O,  is  probably  also  a 
glucose.  It  is  found  in  the  animal  organism  in  the  muscles  of  the  heart, 
and  also  in  many  plants,  e.g.  unripe  beans,  peas  and  lentils.  It  forms 
large  crystals  which  weather  on  exposure,  and  does  not  reduce  Fehling's 
solution. 

Glucosamine,  CgHiiOg(NH2),  is  a  derivative  of  glucose  resulting  from 
the  action  of  dilute  acids  upon  chitin  (p.  518),  (B.  17,  241).  An  isomer, 
iso-glucosamine,  has  already  been  mentioned  (p.  287). 


B.  The  Oane  Sugar  Group,  G^2^22^^v 

To  the  cane  sugar  group  belong  all  the  compounds  of  sweet 
taste,  which  are  converted  into  true  glucoses, 

CgHjgOe*  action  of  dilute  acids,  and  which  are  conse- 

quently to  be  regarded  as  the  anhydrides  of  the  latter ;  also 
raffinose,  GigHggOjg,  which  shows  a  similar  chemical  behaviour. 
The  compounds  of  the  cane  sugar  group  possess  a  sweet  taste, 
crystallize  more  readily  and  are  more  stable  than  the  glucoses, 
but  resemble  the  latter  in  solubility.  They  are  optically 
active.  With  the  exception  of  maltose  they  are  not  directly 
fermentable,  but  only  after  being  broken  up  (see  below),  and, 
with  the  exception  of  milk  and  malt  sugar,  they  either  do  not 
reduce  Fehling^s  solution  or  do  so  only  with  difficulty.  They  are 
split  up  into  glucoses,  with  assimilation  of  water,  when  boiled 
with  dilute  mineral  acids  or  when  subjected  to  the  action  of 
ferments  such  as  diastase  and  soluble  yeast  ferment,  (see  p. 
293) : 

C12H22O11  +  HgO  =  2GqH.^Pq. 

Cane  sugar  is  broken  up  in  this  way  into  equal  quantities 
of  dextrose  and  laevulose.    This  assimilation  of  water  is  termed 

(506)  T 


290 


XIV.  CARBOHYDRATES. 


an  "inversion"  and  the  laevo-rotatory  mixture,  so  obtained, 
invert-sugar,  because  the  original  dextro-rotatory  action  upon 
polarized  light  has  been  reversed.  Milk  sugar  breaks  up  in 
an  analogous  way  into  grape  sugar  and  galactose,  and  maltose 
into  2  mols.  dextrose. 

On  account  of  this  decomposition  into  2  molecules  of  glucoses,  the 
sugars  of  the  above  group  are  also  termed  **-dioses,"  e.g.  milk  sugar 
is  lacto-diose.    Raffinose  may  be  called  a  **  -triose." 

Constitution.  The  compounds  of  the  cane  sugar  group  are 
thus  ethereal  anhydrides  of  the  glucoses,  e.g.  cane  sugar  is 
dextrose-laevulose  anhydride,  and  malt  sugar  dextrose  anhy- 
dride, etc.  In  this  formation  of  anhydride  there  remain  four 
hydroxyls  over  for  every  six  carbon  atoms  of  the  glucose  in 
question,  CgH^0(0H)5,  thus : 

20eH,0(0H),  =  [Q,U,0{OB.),\0  +  H^O; 
hence  cane  sugar  etc.  are  octatomic  alcohols.    In  accordance 
with  this  stands  the  production  of  oct-acetyl  ethers,  O^g-^uOs 
(0. 621130)3,  by  the  action  of  acetic  anhydride. 

Oct-aceto-saccharose  is  also  formed  directly  by  acetylating  a  mixture 
of  dextrose  and  Isevulose,  and  the  oct-acetate  of  milk  sugar  in  an 
analogous  manner  from  dextrose  and  galactose.  These  ethers  may  be 
saponified  by  cautious  treatment  with  baryta  water,  and  cane  and  milk 
sugar  thus  indirectly  synthetized. 

Since  lactose  and  maltose,  in  contradistinction  to  saccharose  (cane 
sugar),  possess  reducing  properties  and  yield  hydrazones,  they  probably 
contain  the  atomic  group — CH(OH) — CO — ,  which  is  altered  in  the  case 
of  cane  sugar  by  the  formation  of  anhydride.    (Fischer,  B.  20,  834.) 

Behaviour,  1.  For  decomposition  by  mineral  acids  and  for- 
mation of  compound  ethers,  see  above. 

2.  They  form  saccharates  Avith  bases,  (see  cane  sugar). 

3.  Fermentation.  Maltose  is  directly  fermentable  by  yeast, 
milk  sugar  only  with  difficulty,  and  cane  sugar  not  at  all  until 
it  has  been  "inverted,'^  which  process  is  effected  by  the  soluble 
yeast  ferment  itself.  Milk  sugar  readily  undergoes  the  lactic 
fermentation. 

4.  Oxidation  gives  rise  to  the  same  products  as  are  obtained  from  the 
glucoses  which  form  their  basis. 


CANE  AND  MILK  SUGARS. 


291 


5.  Cane  sugar  only  reduces  Fehling's  solution  after  inversion, 
maltose  and  milk  sugar  however  upon  boiling;  the  last  named 
also  reduces  an  ammoniacal  silver  solution. 

6.  The  reducing  sugars  form  compounds  with  phenyl- 
hydrazine,  e.g.  phenyl-lactosazone  and  phenyl-maltosazone, 
(B.  17,  580);  cane  sugar,  on  the  other  hand,  is  indifferent 
towards  this  reagent. 

Cane  sugar  or  Saccharose,  saccharobiose,  CigHggOii.  Occurs 
in  red  beet  (Beta),  in  the  sugar  cane  (Saccharum),  in  the 
sugar  millet  (Sorghum),  and  in  many  other  plants,  chiefly  in 
the  stem.  It  crystallizes  in  large  monoclinic  prisms,  as  is 
well  seen  in  sugar-candy,  and  is  soluble  in  one-third  of  its 
weight  of  water.  It  is  not  turned  brown  when  heated  with 
potash,  and  yields  saccharates  with  lime  and  strontia,  e.g. 
C12H22O11  +  CaO  +  2H2O;  C12H22O11  +  2CaO;  0^2^^^^^  +  3CaO. 
These  compounds  are  of  great  value  for  the  working  up  of 
the  uncrystallizable  beet  sugar  mother  liquors  known  as 
molasses.  The  further  action  of  lime  converts  it  into  saccharic 
acid,  which  is  isomeric  with  the  glucoses,  (cf.  B.  16,  1727). 
Concentrated  sulphuric  acid  produces  charring,  (difference 
from  dextrose).  Cane  sugar  melts  at  160°  and  remains  in  the 
amorphous  condition  for  some  time  after  cooling  (barley-sugar) ; 
when  heated  more  strongly,  it  becomes  brown  from  the  form- 
ation of  caramel  or  sugar  dye,  and  finally  chars.  As  already 
mentioned,  it  readily  undergoes  inversion. 

The  percentage  of  sugar  in  a,  solution  of  unknown  strength  (p)  can 
be  determined  from  the  specific  rotatory  power  ([a]^^  =  +  64-1°),  by 
measuring  the  angle  through  which  the  solution  turns  the  plane  of 
polarization  of  a  ray  of  polarized  light  passed  through  it.  This  is 
known  as  Saccharimetry. 

Milk  sugar  or  Lactose,  ladohiose,  C12H22O11  +  H2O,  occurs 
in  milk,  and  only  occasionally  in  the  vegetable  kingdom.  It 
is  obtained  by  evaporating  sweet  whey.  It  crystallizes  in  hard 
rhombic  prisms,  and  is  much  less  sweet  than  cane  sugar,  and 
also  much  less  soluble  in  water.  It  is  converted  into  lacto- 
caramel"  at  186°.    For  its  reducing  power,  see  previous  page. 

Maltose  or  Malt  sugar,  maltohiose,  C^2^22Pi^  +  HgO,  results 


292 


XIV.  CARBOHYDRATES. 


from  the  action  of  diastase  upon  starch  during  the  germination 
of  cereals  (preparation  of  malt),  and  also  as  an  intermediate 
product  on  boiling  starch  with  dilute  sulphuric  acid.  It  forms 
a  hard  white  crystalline  mass,  very  similar  to  grape  sugar,  and 
strongly  dextro-rotatory.  Its  power  of  reducing  Fdiling's 
solution  is  only  about  two-thirds  of  that  of  dextrose. 

Related  to  the  sugar  varieties  of  this  class  is  Raffinose  or  melitose, 
Ci2H220ii  +  3H2O,  which  is  found  in  the  sugar  beet  and  therefore  in 
molasses,  in  the  manna  of  the  eucalyptus,  and  in  cotton  seed  cake,  etc. 
It  is  very  like  cane  sugar  but  tasteless,  polarizes  very  strongly,  does 
not  reduce  FeUing^s  solution,  and  goes  into  galactose  and  Isevulose  on 
inversion. 


0.  The  Cellulose  group,  G^^i^O^, 

The  molecular  formula  of  the  members  of  this  series  must 
always  be  a  multiple  of  the  simple  analysis-formula  CgHj^Og. 
They  are  for  the  most  part  amorphous  and  tasteless,  insoluble 
in  alcohol  and  ether,  partly  soluble  in  cold  water  and  partly 
insoluble ;  thus  cellulose  is  insoluble  and  also  mucilage,  the 
latter  merely  swelling  up  with  water,  while  starch  forms  a  jelly 
with  hot  water.  When  boiled  with  dilute  acids  or  subjected 
to  the  action  of  ferments,  they  break  up  into  glucoses  or 
maltose,  water  being  taken  up,  thus : 

Like  the  foregoing  compounds  therefore,  they  are  to  be 
regarded  for  the  most  part  as  the  anhydrides  of  glucoses. 
Consequently  they  still  possess  an  alcoholic  character  and 
yield  acetic  and  nitric  ethers,  etc.  Most  of  them  are  optically 
active.  Dilute  nitric  acid  forms  the  same  oxidation  products 
with  them  as  result  from  the  corresponding  glucoses,  and  iodine 
frequently  gives  characteristic  colourations. 

Cellulose,  (CgH^oOg),,,  is  widely  distributed  in  nature  as  the 
membrane  of  plant  cells;  cotton,  elder  pith,  wood,  etc.,  consist 
of  cellulose  in  a  more  or  less  pure  state.  It  can  be  prepared 
by  extracting  wadding  or  Swedish  filter  paper  with  caustic 
potash,  hydrochloric  acid,  water,  alcohol  and  ether  successively. 


STARCH. 


293 


It  forms  a  white  amorphous  powder,  insoluble  in  the  ordinary 
reagents  but  soluble  in  an  ammoniacal  solution  of  cupric  oxide, 
from  which  it  is  again  thrown  down  by  acids. 

When  boiled  with  dilute  sulphuric  acid,  it  yields  dextrine  and 
dextrose,  while  the  concentrated  acid  converts  it  first  into  Amyloid, 
an  amorphous  mass  which  is  turned  blue  by  iodine,  and  finally  into 
dextrine.  Parchment  paper  is  simply  unglazed  paper  which  has  been 
transformed  superficially  into  amyloid  by  sulphuric  acid.  A  mixture  of 
nitric  and  sulphuric  acids  gives  rise  to  nitric  ethers,  viz.  (according  to 
the  intensity  of  the  reaction)  either  Gun  cotton  or  Pyroxyline^ 
Ci2H^4(N02)60io,  an  important  explosive,  insoluble  in  alcohol-ether,  or 
Collodion,  which  contains  less  of  the  nitric  radicle,  is  not  so  explosive, 
and  is  soluble  in  alcohol-ether.  Celluloid  is  produced  by  treating 
nitrated  cellulose  with  camphor. 

Starch  or  Amylum,  (C(.Hio05)x,  [Cg^HggOgi  ?],  is  present  in 
all  assimilating  plants,  being  built  up  in  the  chlorophyll 
granules  from  the  carbonic  acid  absorbed,  and  is  found 
especially  in  the  nutriment  reservoirs  of  the  plants,  e.g,  in  the 
grains  of  cereals,  in  perennial  roots,  potatoes,  etc.  It  is  con- 
verted into  sugar  during  the  transference  of  the  sap.  It 
forms  a  white  velvety  hygroscopic  powder  which  consists  of 
round  or  elongated  granules  in  concentric  layers,  insoluble  in 
cold  water.  The  interior  of  these  granules  consists  of  "  granu- 
lose  "  and  their  husk  probably  of  cellulose.  When  they  are 
warmed  with  water,  the  latter  is  broken  open  and  a  jelly 
formed.  Both  the  granules  of  starch  and  its  jelly  are  coloured 
an  intense  blue  by  iodine  and  bright  yellow  by  bromine,  from 
the  formation  of  loose  addition  compounds.  The  colour  of  the 
iodine  starch  paste  vanishes  on  heating  but  reappears  on 
cooling. 

When  heated  with  glycerine,  the  so-called  "  soluble  starch 
is  formed,  also  when  boiled  with  water  containing  sulphuric 
acid  or  by  the  action  of  diastase.  Further  treatment  with 
acid  converts  it  into  dextrine  and  dextrose,  and  with  diastase 
into  dextrine  and  maltose.  Warming  with  very  little  dilute 
nitric  acid  to  110°  yields  dextrine. 

Ferments.  As  has  already  been  repeatedly  mentioned,  starch  is 
transformed  by  the  action  of  diastase  into  maltose  and  dextrine.  This 


294 


XIV.  CARBOHYDRATES. 


diastase  is  an  albuminous  substance  of  unknown  composition  which  is 
termed  an  unorganized  ferment,"  in  contradistinction  to  the  *'  organ- 
ized ferments,"  the  micro-organisms  (p.  80).  It  is  produced  during  the 
germination  of  barley  and  other  varieties  of  cereals,  is  precipitated  as  a 
white  powder  in  the  aqueous  malt  extract,  and  causes  the  conversion  of 
starch  into  sugar  when  added  to  starch  paste.  Among  other  unorganized 
ferments  may  be  mentioned  emulsin,  which  is  contained  in  bitter 
almonds,  the  soluble  ferment  of  yeast,"  the  ptyalin  of  the  saliva,  the 
pepsin  of  the  gastric  juice,  and  the  trypsin  of  the  pancreas. 

The  following  substances,  among  others,  closely  resemble  starch  : 
Lichenin  or  moss  starchy  present  in  many  lichens,  e.g.  in  Iceland 
moss  (Cetraria  islandica),  which  is  coloured  a  dirty  blue  by  iodine  ;  and 
Inulin,  present  in  the  roots  of  the  dahlia  and  many  composites 
(Inula  Helenium),  which  is  coloured  yellow  by  iodine  and  converted 
into  laevulose  when  boiled  with  water. 

Glycogen  or  Animal  starcli,  liver  starch,  is  present  e.g.  in  the  livers  of 
the  mammalia.  It  is  a  colourless  amorphous  powder  which  is  turned 
wine-red  by  iodine  ;  after  the  death  of  the  animal  it  rapidly  changes 
into  dextrose,  the  same  conversion  being  effected  by  boiling  with  dilute 
acids,  while  ferments  transform  it  into  maltose. 

Gum  varieties,  GgH^oOg.  The  gums  are  amorphous  trans- 
parent substances  widely  distributed  in  the  vegetable  world, 
which  yield  sticky  liquids  with  cold  water  and  are  precipitated 
by  alcohol.  The  gums  proper  dissolve  in  cold  water  to  clear 
solutions  while  the  mucilages  only  swell  up  with  water  to  a 
liquid  which  cannot  be  filtered. 

Dextrine  or  starch  gurriy  CgH^oOg,  is  formed  by  heating 
starch  either  alone  or  with  a  little  nitric  acid,  together  with 
dextrose  by  boiling  it  with  dilute  sulphuric  acid,  and  together 
with  maltose  by  diastase.  It  exists  in  various  modifications 
(amylo-dextrine,  erythro-dextrine,  achroo-dextrine,  malto- 
dextrine),  which  differ  from  one  another  in  their  behaviour 
with  iodine.  It  does  not  reduce  Fehling^s  solution  even  when 
warmed,  and  is  not  directly  fermentable  by  yeast  but  only 
after  the  prolonged  action  of  diastase,  maltose  being  formed. 
Its  applications  are  numerous. 

Arabic  acid,  2C6H10O5  -f  HgO.  Gum  arabic  or  arabin,  a  clear  glassy 
secretion  of  many  plants,  which  dissolves  to  a  clear  solution  in  water 
and  is  much  used  as  a  gum,  consists  of  the  potassium  and  calcium  salts 
of  arabic  acid.    The  latter  is  a  white  amorphous  Isevo- rotatory  mass, 


TRANSITION  TO  THE  AROMATIC  COMPOUNDS.  295 


which  is  broken  up  by  dilute  acids  into  arabinose  and  dextrose  ;  it  is 
not  yet  certain  that  it  belongs  to  the  class  of  carbohydrates. 

Bassorin  (a  mucilage),  is  the  chief  constituent  of  gum  tragacanth 
and  gum  bassora. 


XV.  TRANSITION  TO  THE  AROMATIC 
COMPOUNDS. 

In  the  compounds  which  have  been  treated  of  up  to  now,  a 
so-called  open  carbon  chain"  has  been  assumed,  i.e.  one  in 
which  the  end  and  middle  carbon  atoms  have  to  be  distin- 
guished from  one  another.  For  benzene  and  its  extraordinarily 
numerous  derivatives,  on  the  other  hand,  it  is  very  probable 
that  six  carbon  atoms  are  linked  together  in  a  "  closed  chain," 
or,  in  other  words,  that  the  two  end  carbon  atoms  of  the 
original  open  chain  0 — C — C — C — 0 — C  are  now  joined 
together.    Such  a  linking  is  also  termed  a  "  ring,"  (c£  p.  52). 

The  question,  what  kinds  of  closed  carbon  chains  are  capable 
of  existence,  has  therefore  of  late  been  the  subject  of  much 
investigation,  and  it  would  seem — so  far  as  our  present  know- 
ledge goes — that  such  compounds  with  three,  four,  five  and 
possibly  seven  carbon  atoms  can  be  prepared.  The  simplest 
compounds  of  this  nature  which  are  theoretically  possible 
consist  of  three,  four,  or  five  methylene  groups,  viz.,  tri- 
methylene,  CgHg,  tetra-methylene,  C^Hg  and  pentamethylene, 
C^H^o,  the  two  last  being  only  known  in  the  form  of  deriva- 
tives. 

A.  Tri-,  Tetra-,  and  Penta-methylenes. 

Derivatives  of  tri-  and  tetra-methylene,  in  especial  carboxylic  acids, 
e.g.  Tri-methylene-mono-carboxylic  acid,  C3H5CO2H,  Tri-methylene- 
di-carboxylic  acid,  C3H4(C02H)2,  and  Tetra-methylene-di- carboxylic 
acid,  C4H(5(C02H)2,  etc.,  have  been  prepared  (at  first  as  ethers)  by  W. 
H.  Perkin,  jun.,  by  the  action  of  ethylene  bromide  and  tri-methylene 
bromide  upon  sodio-malonic  ether  (see  B.  17,  1652,  etc.,  also  various 
papers  in  Ch.  Soc.  J.),  thus : 


296     XV.  TRANSITION  TO  THE  AROMATIC  COMPOUNDS. 


•    ^     +  NaoC<  =    •    ^>C<  +  2NaBr. 

Such  a  mode  of  formation  points  to  the  atomic  grouping  which  has 
just  been  indicated,  (Cf.  also  Fittig  and  Marburg ^  B.  18,  3413),  as  does 
also  the  fact  that  these  compounds  show  much  less  tendency  to  combine 
with  bromine,  hydrogen  or  hydrobromic  acid  than  the  okfines  or  the 
unsaturated  acids  do.  Bromine  either  does  not  act  at  all  or  adds  itself 
on  with  difficulty,  nascent  hydrogen  is  without  action  and,  although 
combination  with  hydrobromic  acid  is  more  readily  effected,  that  also 
is  relatively  difficult.  Such  an  addition  can,  according  to  theory,  only 
be  brought  about  by  a  breaking  up  of  the  ring,"  i.e.,  by  the  formation 
of  an  open  chain  and  the  taking  up  of  two  monovalent  atoms. 

A  Penta-methylene-dicarboxylic  acid,  C5H8(C02H)2,  has  also  been 
obtained  by  means  of  the  malonic  ether  synthesis,  (B.  18,  3246). 

Leuconic   acid,    or  penta-Tceto-'pentamethylene,    C5O5  +  4H2O,  = 

CO^  ^  and  its  near  relation  Croconic  acid,  CgOgHg,  are  derlva- 

tives  of  penta-methylene.  Both  of  these  have  been  prepared  from 
potassium  carboxide,  a  bye-product  in  the  manufacture  of  potassium, 
and  are  highly  interesting  from  a  theoretical  point  of  view,  (Nietzki 
ajid  BenckiseVf  B.  19,  293;  20,  1617.)    See  hex-oxy-benzene. 

For  Penta-methylene  derivatives,  cf.  also  Fittig ,  B.  18,  3410 ; 
Hantzsch,  B.  20,  2780. 


Closed  chains  which  contain  other  polyvalent  elements 
(0,  S,  N)  in  addition  to  carbon  are  known  in  considerable 
number;  they  must  manifestly  be  assumed,  for  example,  in 

succinic  anhydride,        nr^^^     succinimide,  ^^^^  j>JN, 

CHg — CH2 — 

in  y-butyro-lactone,  |  |     ,   in    parabanic  acid, 

0  00 

alloxan,  etc.,  and  also  in  pyridine,  quinoline,  etc. 

At  this  point  must  be  described  three  compounds  in  which 
closed  atomic  rings  are  likewise  to  be  assumed,  viz. : 


FURFURANK  ;  THIOPHENE  ;  TYRROL. 


297 


B.  Furfurane,  C^H^O,  Thiophene,  C^H^S,  and 
Pyrrol,  C,H4(NH). 


From  these  compounds  a  whole  series  of  derivatives  are  ob- 
tained by  the  substitution  of  hydrogen  by  halogen,  and  also  by 
the  entrance  of  the  groups  — CH3,  — CHgOH,  ~CHO,  — COgH, 
etc.  In  their  properties  furfurane,  thiophene  and  pyrrol 
remind  one  of  benzene.  Thiophene  in  particular  is  delusively 
like  the  latter,  e.g,  in  odour  and  boiling  point,  and  its  various 
derivatives  often  show  a  marvellous  similarity  in  their  chemical 
and  physical  relations  to  the  corresponding  derivatives  of 
benzene.    (See  table,  below.) 

Summary, 


Furfurane, 
C4H4O. 

Pyrrol^ 

Thiophene, 
C4H4S. 

Benzene, 

Dibromo- 
furfurane 
C4H2Br20. 

Tetra-iodo-pyrrol 
C4l4(NH). 

Dibromo- 
thiophene 
C4H2Br2S. 

Dichloro-benzene 
C6H4CI2. 

Methyl -furfurane 

C4H80(CH3). 

a-,  j8-Methyl- 

pyrrol 
C,H3NH(CH3). 

a-,  jS-Methyl- 
thiophene 

C4H3S(CH3). 

Toluene 

Furfurane  alcohol 
C4H30(CH2.0H). 

Thiophene  alcohol 
C4H3S(CH2.0H). 

Benzyl  alcohol 
CeH,(CH2.0H). 

Furfurol 
C4H30(CHO). 

Thiophene 
aldehyde 
C4H3S(CHO). 

Benzoic  aldehyde 
C(,H5(CH0). 

Pyromucic  acid 
C4H30(C02H). 

a-,  ^-Pyrrol- 

carboxylic  acid 
C4H3NH(C02H). 

a-,  /3-Thiophene- 
carboxylic  acid 
C4H3S(C02H). 

Benzoic  acid 
CaH^iCO^H). 

Dimethyl- 
furfurane 
C4H20(CH3),. 

a-,  /3-Dimethyl- 

pyrrol 
C4H2NH(CH3)2. 

Dimethyl- 
thiophene 
641128(0113)2. 

Xylenes 
C6H4(CH3)2. 

Methyl-pyrrol 
C4H4(N.CH3). 


Etc. 

Amido-thiophene 
C4H3S(NH2). 

Thiophene- 
sulphonic  acid 
C4H3S(S03H). 


Aniline 

Benzene- 
sulphonic  acid 


298     XV.  TRANSITION  TO  THE  AROMATIC  COMPOUNDS. 


Furfurane,  pyrrol  and  thiophene  also  resemble  one  another 
in  many  respects.  All  three  boil  at  relatively  low  temperatures, 
(  +  32°,  126°,  84°),  are  either  insoluble  or  only  slightly  soluble 
in  water,  but  easily  in  alcohol  and  ether,  and  show  many 
analogous  colour  reactions.  Thus  pyrrol  and  thiophene  and 
their  derivatives  give,  for  the  most  part,  an  intensive  violet 
to  blue  colouration  when  mixed  with  isatin  and  concentrated 
sulphuric  acid,  and  a  cherry-red  or  violet  colouration  with 
phenanthrene-quinone  and  glacial  acetic  or  sulphuric  acid. 
The  vapour  of  pyrrol  colours  a  pine  shaving  which  has  been 
moistened  with  hydrochloric  acid  carmine  red  (iryppos^  fiery- 
red),  while  furfurol  vapour  colours  it  an  emerald  green;  the 
latter  likewise  colours  a  piece  of  paper  moistened  with  xylidine- 
or  aniline  acetate  red.  Furfurane  is  converted  by  hydrochloric 
acid,  i.e.  by  mineral  acids,  into  an  insoluble  amorphous  powder, 
and  pyrrol  into  an  insoluble  amorphous  brown-red  powder 
^'pyrrol-red"  (with  evolution  of  ammonia),  while  thiophene 
remains  unaltered ;  the  derivatives  show  a  similar  behaviour. 
Pyrrol  is  distinguished  from  the  two  other  compounds  by 
having  weakly  basic  properties. 

Formation.  1.  From  mucic  acid,  C4H4(OH)4(C02H)2.  This 
is  converted  into  pyromucic  acid  (  =  furfurane-carboxylic  acid), 
C4H30(C02H),  upon  dry  distillation,  the  latter  in  its  turn 
yielding  furfurane  when  heated  with  caustic  soda.  By  the 
action  of  ammonia,  i.e.  by  the  dry  distillation  of  the  ammonium 
salt,  mucic  and  pyromucic  acids  are  transformed  into  pyrrol. 
Lastly,  thiophene -carboxylic  acid,  and  from  it  thiophene, 
result  upon  heating  mucic  acid  with  barium  sulphide  : 

(a)  C4H4(OH)4(C02H)2  =  C^H^O      -f  2CO2  +  3H2O ; 

(&)04H4(OH)4(C02H)2  +  NH3  =  C4H4(NH) -h  2CO2  +  4H2O ; 
(c)  G,B,{OB.)^(CO,-B.)^-\-R,S    -C^H^S         2CO2 4- 4H2O. 

2.  From  succinic  acid,  C2H4(C02H)2.  Succinimide, 
C4H402(NH),  yields  pyrrol  when  strongly  heated  with  zinc 
dust,  and  sodium  succinate  yields  thiophene  when  heated  with 
PgSg,  {Folhard-Erdmann,  B.  18,  454.) 

3.  Pyrrol  also  results  from  acetylene  and  ammonia  at  a  red  heat,  and 
thiophene  when  ethylene  is  led  over  glowing  pyrites. 


FURFURANE. 


299 


4.  By  the  action  of  NH3  or  PgSg  respectively  upon  aceto-acetic  ether 
and  diaceto- succinic  ether,  complicated  pyrrol  and  thiophene  derivatives 
are  obtained,  {Knorr,  B.  17,  1635;  18,  307,  1558.) 

5.  From  acetonyl-acetone,  CH3— CO— CH^— CH2— CO— CH3, 
dimethyl-furfurane  results  with  separation  of  water,  dimethyl- 
pyrrol  by  heating  it  with  alcoholic  ammonia,  and  finally 
dimetliyl-thiophene  with  pentasulphide  of  phosphorus,  {Paal, 
B.  18,  58,  367 ;  20,  1074.) 

This  behaviour  would  indicate  that  the  acetonyl-acetone  changes  first 

into  the  isomeric  compound,  CH3— C(OH)-CH— CH=C(OH)— CH3,  or 

CH=C(CH3)(0H)  ...  ^.     ^,     .       ^.       „  .  . 

rN-rr  n,r>TT\fr\TT\  >  ^pou  this  assumption  the  formation  of  dimethyl- 
Cxi=0(CH3)(0H) 

furfurane  appears  simply  as  that  of  an  anhydride,  that  of  dimethyl- 
pyrrol  as  an  exchange  of  2(0H)  for  NH  (imide  formation),  and  that  of 
dimethyl -thiophene  as  the  formation  of  a  sulphide,  i.e.  exchange  of 
2(0H)  for  S,  according  to  the  following  equations  : 

CH=C(CH,).OH  _  CH=C(CH3k 

CH=C(CH3).0H      CH=C(CH3r  ^ 

CH=C(CH3).0H  _  CH=C(CH3k 
+  CH=C(CH3).0H  ~  CH=C(CH3r^"  + 

CH=C(CH3).0H  CH=C(CH,) 
+  CH=C(CH8).0H  CH=C(CH3)^^ 

Prom  the  above  we  have  the  constitutional  formulae  ; 

Furfurane.  Pyrrol.  Thiophene. 

CH=CH^  CH=CH.  CH=CH. 

CH=CH^  CH=CH'^  CH=CH'^ 

((3)  (a) 

These  formulae  receive  corroboration  from  the  frequently  observed 
fact  that  those  substances  are  capable  of  yielding  addition  compounds 
with  bromine  or  hydrogen,  (see  pyrroline).  According  to  the  above 
formulae,  two  isomeric  mono-derivatives  of  each  of  the  three  substances 
are  possible,  e.g.  of  thiophene  :  1.  one  in  which  the  hydrogen  atom 
which  stands  nearest  to  the  S  (0,  or  NH),  and  2.  one  in  which  a  quasi 
middle  hydrogen  atom  is  substituted.  As  a  matter  of  fact  two  such 
isomers  have  been  observed  in  many  cases,  e.g.  two  thiophenic  acids, 
(see  table).  These  crystallize  mixed  together,  the  crystals  having  a 
homogeneous  appearance  although  they  contain  both  acids,  ( V.  Meyer ^ 
A.  236,  200). 

Furfurane,  C4H4O,  is  a  colourless  mobile  liquid  of  chloroform 
odour  which  boils  at  32°.    It  appears  to  be  present  in  pine 


300     XV.  TRANSITION  TO  THE  AROMATIC  COMPOUNDS. 


wood  tar,  as  does  also  Methyl-furfurane  or  sylvane,  B.  Pt.  63°. 
Dimethyl-furfurane,  0^112(0113)20,  is  a  colourless  mobile 
liquid  of  a  characteristic  odour,  B.  Pt.  94°.  Ooncentrated 
acids  convert  it  into  a  resin ;  it  can  be  retransformed  into 
acetonyl-acetone. 

Furfurol,  furfurane  aldehyde,  O^H^Og,  {Ddbereiner)^  results 
from  the  action  of  moderately  concentrated  sulphuric  acid 
upon  carbohydrates,  for  instance,  sugar,  and  is  found  e.g.  in 
fusel  oil.  It  is  a  colourless  oil  of  agreeable  odour  which  is 
turned  brown  by  the  air;  B.  Pt.  162°.  It  has  the  nature  of 
an  aldehyde  and  shows  characteristic  reactions,  (B.  20,  540). 

Pyromucic  acid,  O5H4O3,  =  04H3O(0O2H).  Needles  or 
plates  of  a  character  similar  to  that  of  the  crystals  of  benzoic 
acid,  subliming  easily  and  being  readily  soluble  in  hot  water 
and  alcohol.    M.  Pt.  134°. 

The  furfurane  derivatives  are  frequently  termed  **furane"  deriva- 
tives for  shortness'  sake. 


Pyrrol,  O^H^NH,  is  a  constituent  of  coal  tar  (Bunge)  and 
of  bone  oil  (Anderson),  and  possesses,  like  many  of  its  homo- 
logues,  a  chloroform  odour.  It  is  a  secondary  base.  Its 
imido-hydrogen  is  replaceable  by  alkyl,  acetyl  or  metals. 

Potassium -pyrrol,  C4H4NK,  which  is  obtained  from  pyrrol  and 
potassium  or  potash,  is  a  colourless  compound  which  is  decomposed 
backwards  by  water,  and  which  is  converted  into  pyridine  by  CH2I2 
and  NaO(CH3).  By  the  action  of  iodine  and  alkali,  substitution  takes 
place  with  the  formation  of  Tetra-iodo-pyrrol  or  lodol,  C4l4(NH), 
which  crystallizes  in  yellowish-brown  plates  and  is  an  antiseptic. 

Zinc  and  glacial  acetic  acid  convert  pyrrol  into  Pyrroline,  C4Hg(NH), 
a  colourless  liquid  and  strong  secondary  base,  B.  Pt.  90° ;  and  when 
this  latter  is  heated  with  hydriodic  acid,  it  is  further  reduced  to 
Pyrrolidine,  C4H8(NH),  a  colourless,  strongly  alkaline  base  resembling 
piperidine,  and  boiling  at  85-88°.  Pyrrolidine  yields  pyrrolylene, 
C4H6,  with  methyl  iodide  and  caustic  alkali,  (see  Conine;  also  p.  57.) 
Pyrrolidine  is  formed  synthetically  by  treating  ethylene  cyanide  with 
sodium  and  alcohol,  thus  : 
CH,-CN  ^  _  CH,-CH2.NH,  _  CH,-CH,.  _ 
CH^-CN  ^     "  ~  ~  CH^-CHa-^^     ^  " 

it  is  consequently  designated  Tetra-methylene-imine,  {Ladenburg, 
B.  19,  782  ;  20,  442). 


THIOPHENE. 


301 


PyrocoU,  CgHgNO,  (yellow  plates),  the  anhydride  of  a-Pyrrol- 
carboxylic  acid,  C4H 3^11(00211),  results  from  the  distillation  of  gelatine. 
The  acid  itself  crystallizes  in  metallic  green  prisms,  M.  Pt.  191°.  (Cf. 
table  of  pyrrol  derivatives,  also  B.  20,  2594.) 

Thiophene,  C4H4S,  (K  Meyer,  B.  16,  1465  etc.),  is  likewise 
present  in  coal  tar,  being  invariably  found  in  benzene  (up  to 
0*5  p.c.) ;  the  same  applies  to  its  homologues  thiotolene 
(methyl-thiophene),  and  thioxene  (dimethyl-thiophene),  which 
accompany  toluene  and  xylene,  etc.  Its  boiling  point  (84°)  is 
almost  the  same  as  that  of  benzene  (80-4°),  from  which  it  is 
extracted  by  repeated  shaking  up  with  small  quantities  of 
concentrated  sulphuric  acid,  which  chiefly  dissolves  the  thio- 
phene (to  sulphonic  acid).  (Cf.  B.  17,  2641,  2852.)  It  is  also 
attacked  more  readily  than  benzene  by  other  reagents  such 
as  iodine  and  bromine. 

Thiophene  is  also  obtained  synthetically  by  leading  the  vapour  of 
ethyl  sulphide  through  a  red-hot  tube  (KekuU),  and  in  small  quantity 
by  heating  crotonic  acid,  normal  butyric  acid,  para-aldehyde,  erythrite, 
ether  etc.  with  P2S5. 

The  preparation  and  properties  of  the  thiophene  derivatives 
are  in  part  almost  literally  the  same  as  those  of  benzene. 
Thus  nitric  acid  acts  on  thiophene  to  produce  a  Nitro- 
thiophene,  analogous  to  nitro-benzene,  which  can  in  its  turn 
be  reduced  to  amido-thiophene  ;  the  latter  is,  however,  much 
less  stable  than  the  corresponding  amido-benzene  (aniline). 

Thiophene-sulphonic  acid,  641138(80311),  decomposes  into 
thiophene  and  sulphuric  acid  when  superheated  with  water. 

Thiotenol,  C4H2S(CH3)(OH),  the  phenol  of  thiotolene,  is  formed  by 
heating  levulinic  acid  with  P2S5,  (B.  19,  553). 

The  blue  colouration  which  results  upon  shaking  up  benzene  contain- 
ing thiophene  with  isatin  and  concentrated  H2SO4,  depends  on  the  for- 
mation of  the  blue  colouring  matter  "  Indophenin, "  C12H7NOS. 
CH  CH 

Penthiophene,  ^■^2<Cch=CH^^'  would  be  an  analogue  of  thio- 
phene containing  five  atoms  of  carbon.  A  methyl  derivative  of  it  has 
recently  been  prepared,  which  shows  exactly  the  same  character  and 
colour  reactions  as  thiophene,  but  is  completely  decomposed  by  KMn04. 

(Cf.  F.  Meyer's    Die  Thiophengruppe,"  Braunschweig,  1888.) 


302      XV.  TRANSITION  TO  THE  AROMATIC  COMPOUNDS. 


O.  Pyrazols  and  Thiazols. 

By  the  action  of  phenyl-hydrazine  upon  aceto-acetic  ether,  water 
and  alcohol  are  eliminated  and  there  is  formed  a  compound  CioHioNgO, 
which  was  formerly  considered  to  be  a  quinoline  derivative,  methyl- 
oxy-quinizine,"  but  which  very  probably  possesses  the  constitutional 

Qjj  Q  jq* 

formula       ^    •        nr^^ — CJgHg.    According  to  this  view  it  appears 
0x12 — 

CH=N 

as  a  derivative  of  the  as  yet  unknown  pyrazol,    •  ^NH, 

0x1= OH^ 

(which  is  derivable  from  pyrrol  by  the  exchange  of  CH"'  for  N'")>  and 
has  received  the  name  * '  Phenyl-methyl-pyrazolone  "  on  account  of  its 
possessing  a  ketonic  character.  When  methylated,  it  goes  into  the 
valuable  febrifuge  : 

Antipyrine,  phenyl-dimethyl-pyrazolone,  CnHigNgO,  the  hydro- 
chloride of  which  crystallizes  in  thick  colourless  prisms.  For 
the  constitution  of  these  compounds  see  i.  Knorr,  A.  238,  137. 

All  the  compounds  which  are  constituted  similarly  to  aceto-acetic 
ether  (/3-ketonic  acids,  j8-ketonic  aldehydes,  j8-diketones),  likewise 
yield  derivatives  of  pyrazol  with  phenyl-hydrazine. 

CH— N 

As  derivatives  of  the  as  yet  unknown  TMazol,  ••        ^CH,  (which 

CM — o 

is  derivable  from  thiophene  by  the  exchange  of  CH  for  N),  are  regarded 
a  series  of  peculiar  compounds  which  nearly  resemble  the  bases  of  the 
pyridine  series  in  properties,  and  which  in  fact  are  derived  from  these 
latter  in  the  same  way  as  thiophene — which  so  closely  resembles  benzene 
— is  from  the  latter,  i.e.  by  the  exchange  of  CgHg  for  S.    To  this  class 

belongs  e.g.  Dimethyl-thiazol,       ^    'A    a      — ^-^3>  which  is  formed 

from  monochlor-acetone  and  aceto-thiamide  (p.  ),  with  elimination 
of  HgO  and  HCl,  and  which  is  exceedingly  like  a-lutidine  (dimethyl- 
pyridine,  p.  487),  especially  in  odour  and  basic  character. 

Amido-thiazol,  thiazoline,   ••  — NHg,  which  is  produced  by 

0x1 — o 

the  action  of  mono-chloraldehyde  upon  thio-urea,  is  a  base  of  perfect 
*' aromatic"  character,  like  that  of  aniline.  (Cf.  Hantzsch  and  Weber j 
B.  20,  3118  ;  21,  938,  942). 


THE  BENZENE  DERIVATIVES. 


ao3 


Class  II.— CHEMISTRY  OF  THE 
BENZENE  DERIVATIVES. 

XVI.  SUMMARY. 

All  the  compounds  which  have  been  treated  of  up  to  now 
are  derivable  from  the  homologous  hydrocarbons  GJi2n+2y 
CnHgn,  Ci,H2n-2j  ^tc.  by  the  exchange  of  hydrogen  for  halogen, 
hydroxyl  or  oxygen,  amide,  carboxyl,  etc.  ;  and  since  all  the 
hydrocarbons  already  mentioned  may  also  be  regarded  as  deri- 
vatives of  methane  (e.g.  C^^e  -  ^^^3(0113)  =  methyl-methane, 
C3H8  =  CH2(CH3)2  =  dimethyl-methane,  G^U^  =  CH2  :  CHg 
=  methylene-methane,  C2H2  =  CH  •  CH  =  methine-methane, 
etc.),  we  may  term  the  compounds  which  have  been  described 
in  the  foregoing  portion  of  this  book  Methane  derivatives. 

But  in  addition  to  this  first  class  of  organic  compounds 
there  is  a  second  great  class,  viz.  that  of  the  Aromatic  com- 
pounds or  Benzene  derivatives.  The  first  of  these  two  names  is 
historical  but  no  longer  justified  by  facts,  since  compounds  of 
agreeable  as  well  as  unpleasant  odour  are  to  be  found  in  both 
classes.  As  benzene  derivatives  are  designated  the  members 
of  this  class  which  are  derivable  from  the  hydrocarbon 
benzene,  CgH^  (and  also  from  more  complicated  hydrocarbons 
such  as  anthracene,  naphthalene,  etc.,  which  are  themselves 
derivatives  of  benzene),  just  as  the  methane  derivatives  are 
from  methane. 

Benzene  is,  as  its  formula  CgHg  shows,  a  compound  much 
poorer  in  hydrogen  than  the  paraffins,  containing  eight  H-atoms 
less  than  hexane,  C^H^^ ;  in  the  same  way  all  benzene  deriva- 


304  BENZENE  DERIVATIVES.     XVI.  SUINIMARY. 


tives  are  much  poorer  in  hydrogen,  i.e.  richer  in  carbon  than 
the  analogous  methane  derivatives,  as  is  seen  by  comparing 
e.g.  benzoic  acid,  C^HgOg,  with  heptoic  acid,  C^H^^Og,  or 
aniline,  C^^H^N,  with  ethylamine  C2H^N,  etc.  etc. 

The  hydrogen  atoms  of  benzene  are,  like  those  of  methane, 
replaceable  by  the  most  various  elements  and  atomic  groups. 
By  the  entrance  of  halogens,  substitution  products  result,  by 
the  entrance  of  NHg,  aromatic  bases,  of  OH,  phenols,  of  NOg, 
nitro-compounds,  and  of  CH3  etc.,  the  homologues  of  benzene  ; 
there  are,  in  addition  to  these,  aromatic  alcohols,  aldehydes, 
acids  etc.    (See  table  on  following  page.) 

These  benzene  derivatives  are  partly  analogous  in  their 
properties  to  the  methane  derivatives  of  corresponding  com- 
position ;  in  part,  however,  they  show  new  and  peculiar 
properties  of  their  own,  (see  pp.  306,  333,  359).  One  dis- 
tinguishes between  mono-,  di-,  tri-,  etc.  benzene  derivatives 
according  as  one  or  two  or  more  hydrogen  atoms  are  replaced 
by  the  elements  or  groups  in  question ;  thus,  for  instance, 
toluene  and  chloro-benzene  are  mono -derivatives,  dimethyl- 
benzene  and  dichloro-benzene  di-derivatives,  and  so  on. 
Further,  just  as  it  was  found  when  speaking  of  the  polyatomic 
alcohols  and  acids,  that  the  replacing  groups  need  not  be 
identical,  so  in  this  class  also  innumerable  compounds  are 
known  containing  various  substituents.  Such  compounds 
have  usually  some  of  the  characteristics  of  all  those  mono- 
derivatives  which  result  from  benzene  by  the  exchange  of  one 
H-atom  for  one  of  these  substituents. 

All  the  derivatives  of  benzene  can  be  converted  either  into 
benzene  itself  or  into  very  nearly  allied  compounds  by  rela- 
tively simple  reactions.  Thus  all  the  carboxylic  acids  of 
benzene  (benzoic,  phthalic,  mellitic,  etc.),  yield  benzene  on 
distillation  with  lime,  while  other  acids,  such  as  salicylic,  give 
up  CO2  and  yield  phenol,  and  so  on ;  the  last-named  com- 
pound goes  into  benzene  when  distilled  with  zinc  dust.  The 
homologues  of  benzene  are  converted  by  oxidation  into 
benzene-carboxylic  acids,  which  give  benzene  when  heated 
with  lime. 


BENZENE  DERIVATIVES;  SUMMARY. 


305 


The  relation  of  a  benzene  derivative  to  its  mother  substance  is 
\  therefore  a  very  simple  one, 

!  This  circumstance  is  one  particularly  worthy  of  note,  since  the 
atomic  group  CqH^  is  already  a  tolerably  complicated  molecule  in  itself, 
and  also  because  benzene  cannot  by  any  means  be  transformed  into  a 
simpler  hydrocarbon  containing  5,  4,  or  3  C-atoms  ;  when  oxidized, 
which  is  a  matter  of  difficulty,  it  goes  into  carbon  dioxide  or  similar 
simple  organic  acids. 


Summary  of  a  few  Benzene  derivatives. 


Methyl-benzene  or 

C(5H4(CH3)2 

QH3(  0113)3 
Trimethyl-benzenes. 

Dimethyl-benzenes 

toluene. 

or  xylenes. 

C,H,.C1 

C6H4CI2 

Chlorobenzene. 

Dichloro-benzenes . 

CeH^tOH)^ 

C6H3(OH)3 

Phenol. 

Resorcin,  etc. 

Pyrogallol,  etc. 

C,H5.CH2.0H 

Benzyl  alcohol. 

C6H3(N02)20H 

Nitrobenzene. 

Dinitro -benzenes. 

Dinitro-phenols. 

CeH4(NH2),_ 

.  CeH3(NH2)3 

Aniline. 

Phenylene  diamines. 

Tri-amido-benzenes. 

CgTl5.  SO3H 
Benzene-sulphonic  acid. 

C6H4(NH2)(S03H) 

Benzene-tri-sulphonic 
acid. 

Sulphanilic  acid,  etc. 

CeHs— CHO 
Benzaldehyde. 

C„H5.00,H 

96^3(00211)3 

Benzoic  acid. 

Phthalic  acids. 

Hemi-mellitic  acid,  etc. 

C6H4(OH)(C02H) 
Salicylic  acid,  etc. 

Benzo-nitrile. 

The  benzene  derivatives  are  connected  with  one  another  by 
the  most  various  reactions.  The  NOg-group  is  readily  con- 
vertible into  NH2,  and  the  latter  is  replaceable  by  halogen, 
hydrogen  and  hydroxyl ;  the  halogen  is  also  replaceable  by 
methyl,  carboxyl,  etc. 


(606) 


u 


306  BENZENE  DERIVATIVES.     XVI.  SUMMARY. 


Differences  between  the  aromatic  and  fatty 
hydrocarbons. 

Benzene  differs  from  the  fatty  hydrocarbons  by  the  follow- 
ing reactions  in  particular  : 

1.  It  forms  nitro-benzene  with  nitric  acid  : 

CeHg  +  HO.NO2  =  CfiH^.NOg  +  H^. 

2.  It  yields  benzene-sul phonic  acid  with  sulphuric  acid  : 

C.Hg  +  HO.SO3H  =  C6H,(S03H)  +  H2O. 

Similarly,  almost  all  the  benzene  derivatives  are  capable  of 
forming  nitro-compounds  and  sulphonic  acids  in  nearly  theor- 
etical quantity. 

As  has  been  already  seen,  the  paraffins  are  either  unaffected  by  con- 
centrated HNO3  or  H2SO4,  or  only  attacked  with  difficulty,  while  the 
olefines  form  addition  products  with  the  latter  acid,  without  separation 
of  water. 

3.  The  homologues  of  benzene  differ  from  the  paraffins 
especially  in  their  capability  of  oxidation  ;  while  the  latter  are 
only  attacked  with  difficulty  by  oxidizing  agents,  the  former 
are  readily  converted  into  benzene-carboxylic  acids. 

There  are  not  wanting  other  distinguishing  characteristics 
between  the  aromatic  hydrocarbons  and  the  paraffins.  Thus  the 
halogen  compounds  C^H^X  are  less  active  chemically,  and  the 
hydroxyl  compounds,  e.g.  C^^{OYi.),  are  of  a  more  acid  nature 
than  the  corresponding  fatty  bodies  ;  further,  diazo-compounds 
are  known  almost  only  in  the  aromatic  series,  etc. 

V.  Meyer  defines  as  "  aromatic  "  hydrocarbons  such  as  are  nitrated 
by  nitric  acid,  converted  into  sulphonic  acids  by  sulphuric  acid,  sub- 
stituted by  bromine  with  the  formation  of  stable  products,  and  trans- 
formed into  ketones  (p.  399)  by  organic  acid  chlorides  together  with 
chloride  of  aluminium.  The  compounds  derived  from  these  are 
aromatic"  compounds.  Thiophene,  which  behaves  in  a  manner 
exactly  analogous  to  benzene,  is  thus  also  an  aromatic  compound. 


Characteristic  of  the  benzene  derivatives  are  their 


ISOMERISM  IN  THE  BENZENE  SERIES. 


307 


Isomeric  relations. 

1.  While  several  isomeric  mono-derivatives  are  both  theor- 
etically possible  and  have  been  practically  obtained  from  each 
hexane,  CgH^^,  benzene  is  only  capable  of  forming  a  single 
mono-derivative  in  each  case  ;  isomeric  mono-derivatives  of 
benzene  are  unknown.  The  six  hydrogen  atoms  of  benzene  thus 
possess  an  equal  value.  This  is  not  merely  an  empirical  law, 
but  one  which  has  been  proved  experimentally. 

Proof  of  the  equal  value  of  the  six  hydrogen  atoms. 

Let  the  six  H-atoms  be  designated  as  a,  &,  c,  d,  e  and  /  respectively. 

1.  Phenol,  C6H5(OH),  whose  hydroxyl  may  have  replaced  the 
H-atom  a,  may  be  converted  into  bromo-benzene,  CgHgBr,  and  this 
latter  into  benzoic  acid,  CeHglCOgH).  The  carboxyl  in  the  latter  has 
therefore  also  the  position  a,  i.e.  it  has  replaced  the  H-atom  a. 

2.  The  three  existing  oxy-benzoic  acids,  C6H4(OH)(C02H),  can 
either  be  prepared  from  benzoic  acid  or  converted  into  it ;  their  carboxyl 
therefore  has  the  position  a,  and  consequently  their  hydroxyl  must 
replace  some  one  of  the  other  H-atoms,  be  it  b,  c,  or  d. 

3.  The  oxy-benzoic  acids  can  all  give  up  carbon  dioxide,  yielding 
thereby  the  same  phenol,  CgHgOH,  in  every  one  of  the  three  cases  : 

C6H4(OH)(C02H)  =  CgHglOH)  +  COg. 

And  since  the  latter  compound  contains  the  hydroxyl  in  position  a, 
according  to  1,  while  the  hydroxyl  in  the  oxy-benzoic  acids  replaces  the 
H-atoms  6,  c  and  d,  it  follows  that  the  hydrogen  atoms  a,  6,  c  and  d 
are  of  equal  value. 

4.  Now,  as  will  be  explained  on  p.  308,  there  are  present  for  each 
H-atom  two  other  pairs  of  similarly-linked  or  symmetrical  hydrogen 
atoms,  i.  e.  pairs  of  which  either  the  one  or  the  other  may  be  replaced 
by  any  given  atomic  group,  without  different  substances  resulting. 
But  the  atoms  of  such  a  pair  cannot  be  present  in  the  positions  a,  6,  c 
and  dj  as  in  this  case  three  oxy-benzoic  acids  could  not  exist.  It  must 
therefore  be  the  remaining  H-atoms  e  and  /  which  are  respectively 
united  symmetrically  to  one  of  the  former,  and  which  are  therefore  of 
equal  value  with  them,  e.g.  e  =  f  =  b.  Since,  however,  a  =  b  =  c  =  d, 
it  follows  that  all  the  six  hydrogen  atoms  are  of  equal  value,  (Laden- 
burg,  B.  7,  1684.) 

2.  If  two  hydrogen  atoms  in  benzene  are  replaced  by  other 
elements  or  groups,  so  that  di-derivatives  result,  these  latter 


308  BENZENE  DERIVATIVES.     XVI.  SUMMARY. 


must  exist  in  three  different  isomeric  forms.  We  have  thus 
three  di-chloro-benzenes,  CgH^Clg,  three  di-amido-benzenes, 
CgH4(N"H2)2,  three  di-methyl-benzenes,  GqH.^{GB.^)2,  three  oxy- 
benzoic  acids,  CgH4(OH)(C02H),  and  so  on.  And  this  is  no 
mere  empirical  law,  for  it  has  been  proved  that  only  three 
isomeric  di-derivatives  of  benzene  are  capable  of  existence. 

It  can  be  shown  that  for  each  H-atom  of  benzene,  e.g.  for  a, 
two  other  pairs  of  H-atoms,  e.g.  b  and  /,  c  and  e,  are  symmetri- 
cally linked,  so  that  it  makes  no  difference  whether,  after  a  is 
replaced,  the  second  substituent  replaces  the  one  or  the  other 
of  the  symmetrically  linked  hydrogen  atoms.  According  to 
the  above  notation,  therefore,  ab  =  af,  and  ac  =  ae.  On  the 
other  hand  the  combinations  ab  and  ac  are  not  equivalent  but 
represent  isomers ;  the  combination  ad,  the  only  remaining 
case,  represents  the  third  isomer. 

Proofs,  that  for  every  H-atom  {a)  two  other  pairs  of 
symmetrically  hnked  H-atoms  exist, 

have  been  advanced  by  various  scientists,  especially  by  Ladenburg. 
One  of  these  may  be  shortly  sketched  here. 

1.  According  to  Huhner  and  Petermann  (A.  149,  129  ;  cf.  also 
Hiibner,  A.  222,  68,  166),  the  (so-called  meta-)  bromo-benzoic  acid, 
which  is  obtained  by  brominating  benzoic  acid,  and  whose  Br-atom  may 
be  in  position  c  and  COgH  in  position  <x,  yields  with  nitric  acid  two 
nitro-bromo-benzoic  acids,  C6H3Br(N02)(C02H),  the  NOg  being  (say) 
in  positions  h  and  f.  These  are  both  reduced  by  nascent  hydrogen  to 
the  same  (so-called  ortho-)  amido-benzoic  acid,  C6H4(NH2)(C02H),  the 
NO2  being  here  changed  to  NH2  and  the  Br  replaced  by  H.  Since  the 
same  amido-benzoic  acid  results  in  both  cases,  notwithstanding  that  the 
nitro  groups  must  be  in  the  place  of  different  H-atoms  (say  h  and  /) 
from  the  fact  of  the  two  nitro -acids  being  dissimilar,  it  follows  that 
h  and  /  must  be  linked  symmetrically  to  the  H-atom  a,  L  e.  ah  =  af. 

2.  In  an  analogous  manner  the  oxy-benzoic  acid  (salicylic  acid), 
which  can  be  prepared  from  the  above-mentioned  amido-benzoic  acid, 
yields  two  nitro-derivatives  C6H3(OH)(]S'02)(C02H).  If,  however,  the 
hydroxyl  in  these  is  replaced  by  hydrogen  (a  reaction  which  can  be 
effected  by  indirect  methods),  the  resulting  nitro-benzoic  acids, 
C6H4(N02)(C02H),  are  identical,  and  therefore  the  H-atoms  which 
have  been  replaced  by  NO2  are  in  a  position  symmetrical  to  a.  When 
this  nitro-benzoic  acid  is  in  its  turn  reduced  to  amido-benzoic  acid, 


ISOMERISM  OF  THE  BENZENE  DI-DERIVATIVES.  309 


C6H4(N.H2)(CO.^H),  it  is  not  the  above  (ortho-)  amido-acid  (where 
ab  =  a/)  which  is  obtained,  but  an  isomer.  The  NO^-groups  cannot 
therefore  here  be  in  the  position  &=/,  but  must  replace  two  other 
H-atoms  which  are  likewise  symmetric  towards  a,  say  c  and  e,  i.e. 
ac  =  ae.    {HuhneVy  A.  195,  4.) 

Thus  two  pairs  of  H-atoms  are  symmetrically  linked  as  regards  the 
H-atom  a\ah  =  af;  ac  =  ae.  There  only  now  remains  the  third  possible 
combination  ad  ;  the  sixth  H-atom  d  is  situated  towards  the  first  a  in  a 
position  of  its  own,  i.e.  in  one  to  which  there  is  no  corresponding 
position. 

For  further  particulars  cf.  Ladenhurg,  *'  Theorie  der  aromat. 
Verbindungen,"  Braunschweig,  1876  ;  Wroblewsky,  A.  168,  153  ;  192, 
196  ;  B.  8,  573  ;  9,  1055  ;  18,  Ref.  148. 

It  has  been  assumed  in  the  considerations  just  detailed  that 
when  one  compound  is  converted  into  another  by  the  exchange 
of  atoms  or  atomic  groups  (NHg  for  NO2,  H  for  OH),  this 
exchange  is  effected  without  a  so-called  "  molecular  rearrange- 
ment" taking  place  at  the  same  time  (see  p.  166).  Experience 
has  proved  that  this  may  be  taken  for  granted  in  a  large 
number  of  reactions  which  proceed  with  relative  exactitude 
and  at  comparatively  low  temperatures.  Those  instances  in 
which  a  molecular  rearrangement  ensues  are  now  well  known; 
especially  is  this  the  case  in  the  fusion  of  sulphonic  acids 
with  potash  (exchange  of  SO3H  for  OH),  a  reaction  which 
only  takes  place  at  relatively  high  temperatures,  and  which 
frequently  leads  to  isomers  of  the  compounds  expected."^ 

Ortho-,  Meta-  and  Para-  Di-derivatives. 

Just  as  the  mono-derivatives  of  benzene  can  be  transformed 

*  Such  a  rearrangement  of  the  atoms  in  the  molecule  takes  place 
especially  at  rather  high  temperatures.  Thus,  when  potassium  ortho- 
oxybenzoate  is  heated  to  220°,  the  potassium  salt  of  the  para-acid  results ; 
the  three  isomeric  bromo-benzene-sulphonic  acids,  CgH4Br(S03H),  and 
the  three  bromo-phenols,  C6H4Br(OH),  yield  only  meta-dioxy-benzene 
(resorcin)  C6H4(OH)2,  when  fused  with  potash,  and  not  all  the  three 
dioxy  benzenes  ;  and  ortho-phenol-sulphonic  acid,  CgH4(OH)S03H, 
goes  into  the  para-acid  when  heated,  and  so  on.  Reactions  of  this 
nature  probably  arise  from  the  successive  taking  up  and  splitting  off  of 
atoms  or  atomic  groups,  (see  crotonic  acid,  p.  165). 


310 


BENZENE  DERIVATIVES.     XVI.  SUMMARY. 


into  one  another,  so  from  one  di-derivative,  e.g,  G^^(^0^^, 
can  others,  e.g.  G^YL^li^YL^)^,  be  prepared.  And  since  all  the 
di-derivatives  of  benzene  exist  in  three  modifications,  they 
arrange  themselves  into  three  great  classes,  according  to  their 
connection  with  and  convertibility  into  one  another.  Within 
each  of  those  three  classes  the  individual  members  are  related 
by  the  most  various  reactions. 

In  accordance  with  a  proposal  made  by  Korner  (though 
upon  grounds  which  are  no  longer  tenable),  the  above  three 
classes  of  di-derivatives  are  termed  Ortho-,  Meta-  and  Para- 
compounds,  being  written  for  the  sake  of  shortness  with  the 
letters  o-,  m-,  and  p-.  Thus,  (?-diamido-benzene  is  that  one 
which  results  from  the  reduction  of  (?-dinitro-benzene.  It  can 
be  proved  experimentally  (p.  314)  that  the  ortho-  and  meta- 
positions  of  the  H-atoms  are  those  which  occur  in  the  molecule 
in  pairs,  while  there  is  no  position  symmetrical  to  the  para- 
position.  There  are  likewise  experimental  data  for  distin- 
guishing the  ortho-  and  meta-compounds  from  one  another, 
(see  p.  314). 

Isomeric  Tri-  etc.  derivatives. 

With  regard  to  the  tri -derivatives  of  benzene,  CgHgXg,  there 
are  likewise  always  three  isomers  when  the  three  hydrogen 
atoms  are  replaced  by  the  same  substituent,  these  being 
distinguished  on  theoretical  grounds  as  v-,  s-,  and  a-compounds 
(p.  314).  When,  however,  only  two  of  the  substituents  are  the 
same,  there  are  six  isomers,  and  when  all  three  are  different, 
ten.  Of  tetra-derivatives,  CgHgX^,  with  the  same  substituent, 
there  are  likewise  three,  and  of  penta-  and  hexa-derivatives  only 
one ;  these  last  three  classes  may  of  course  be  looked  upon  as 
di-  or  mono-derivatives  of  a  completely  substituted  benzene,  or 
as  the  latter  itself.  When  the  substituents  are  not  the  same, 
many  cases  of  isomerism  are  known. 


CONSTITUTION  OF  BENZENE. 


311 


Constitution  of  Benzene ;  the  Benzene  Theory. 

The  views  which  are  at  present  held  as  to  the  constitution 
of  benzene  and  its  derivatives  rest  principally  upon  KekuU's 
benzene  theory  (1866),  which  has  found  almost  universal 
acceptance  on  account  of  the  elegance  with  which  it  explains 
known  facts,  (see  KehuU,  "Lehrbuch  der  organischen  Chemie,'' 
II.,  493 ;  A.  137,  129).  Since  its  first  proposal  by  him,  it  has 
found  further  support  and  confirmation  from  numberless 
researches.    Its  chief  points  are  the  following : 

1.  The  equal  value  of  the  six  hydrogen  atoms  of  benzene 
and  the  existence  of  three  isomeric  di-derivatives  would  be 
incomprehensible  if  an  open  C-atom  chain  were  ascribed  to  it, 
as  in  the  case  of  the  fatty  compounds.  The  requirement  that 
all  the  H-atoms  of  benzene  shall  be  linked  in  a  precisely  similar 
manner  can,  however,  be  immediately  fulfilled  if  one  assumes 
that  the  first  and  last  atoms  of  the  six-atom  carbon  chain  are 
bound  together  exactly  as  the  remaining  atoms  are  among 
each  other,  Le.  that  the  atoms  form  a  closed  chain"  or  a 
"ring"  (pp.  52  and  295),  thus : 


C-C-C-C-C-C, 

!  I 


Since,  according  to  this  mode  of  combination,  all  the 
C-atoms  are  similarly  grouped,  the  six  H-atoms  can  also  be 
linked  to  them  symmetrically. 

2.  The  further  condition,  that  the  benzene  formula  which  is 
put  forward  shall  render  explicable  the  existence  of  three 
isomeric  di-derivatives,  is  only  fulfilled  if  one  C-atom  binds 
one  H-atom,  i.e.  if  six  CH-groups  are  joined  together  in  ring 
form. 

Leaving  aside  in  the  meantime  the  question  as  to  how  the 
C-atoms  are  connected  by  their  fourth  affinities,  we  obtain  the 
following  graphical  formula  for  benzene  : 


I  I   "  Benzene  ring. " 


312 


BENZENE  DERIVATIVES.     XVI.  SUMMARY. 


H 


H 


HC 


CH 


H 


H 


or,  more  shortly, 


Ha 


\  / 


H 


5  3 


H 


V/ 


H 


H 


This  "hexagon  formula"  is  frequently  made  use  of,  on 
account  of  the  perfect  symmetry  to  which  it  gives  expression. 

3.  We  also  arrive  in  the  following  manner  at  the  conclusion 
that  the  carbon  atoms  of  benzene  form  a  closed  chain.  Benzene 
and  its  derivatives  are  capable  of  forming  addition  compounds, 
although  with  far  more  difficulty  for  the  most  part  than 
ethylene,  for  instance ;  they  can  take  up  two,  four  or  six 
atoms  of  hydrogen,  chlorine  or  bromine,  according  to  the 
conditions  of  the  experiment.  Thus  benzene,  for  example, 
yields  hexa-hydro  benzene,  CgH^g,  upon  prolonged  treatment 
with  hydriodic  acid,  and  the  phthalic  acids,  CgH4(C02H)2, 
yield  di-,  tetra-,  and  hexa-hydro-phthalic  acids,  etc.  The 
resulting  hexa-hydro-compounds  can  not  only  not  combine 
with  any  more  hydrogen  or  halogen,  etc.,  but  they  readily 
give  up  the  added  atoms  upon  oxidation.  Again,  benzene 
hexa-chloride,  C^^^HgClg,  cannot  be  made  to  take  up  more 
hydrogen  or  chlorine  by  any  means,  but  on  the  contrary  it 
readily  yields  up  3H  and  301.  These  compounds  therefore 
differ  materially  from  the  olefines  or  their  derivatives  with 
which  they  are  isomeric. 

The  incapacity  of  hexa -hydro-benzene  to  combine  with  more 
hydrogen  leads  unconstrainedly  to  the  following  constitu- 
tional formula,  according  to  which  it  appears  as  hexa- 
methylene : 


H.C 


CHa 


H^C 


CH2 


KEKULE^S  BENZENE  THEORY. 


313 


4.  The  above  graphical  formula  for  benzene  allows  of  a  very 
simple  explanation  of  the  fact  that  two  pairs  of  symmetrically 
linked  C-atoms  (2  and  6,  3  and  5)  exist  for  each  C-atom  (1), 
and  that  one  of  the  modes  of  combination  of  two  C-atoms 
(1  and  4)  can  occur  only  once  in  the  molecule.  The  existence 
of  three  di-derivatives  is  also  explained  very  easily  thereby, 
for,  according  to  this  formula,  only  three  classes  of  di-deriva- 
tives are  possible,  viz. :  1.  those  whose  substituents  (R)  are 
linked  to  "neighbouring''  C-atoms  (1,  2  =  1,  6);  2.  those 
whose  substituents  are  linked  to  two  C-atoms  which  are 
"separated"  by  a  third  one  (1,  3  =  1,  5);  and  3.  those  whose 
substituents  replace  "opposite"  C-atoms  (1,  4).  These  three 
varieties  of  isomers  are  designated  shortly  as  follows  : 


R 


R 


R 


R 
/\ 


V 


The  existence  of  isomeric  tri-  etc.  derivatives  of  benzene  is  likewise 
readily  explained  by  the  above  formula  ;  when  the  substituents,  R, 
are  the  same,  the  following  cases  are  possible  for  tri- derivatives  : 


R 


R 


R 


R 


R 


R 


R 


R 


R 


In  tri-derivatives  of  the  first  kind  the  three  substituents  are  linked 
to  neighbouring  or  "  vicinal"  {v)  carbon  atoms,  in  those  of  the  second 
to  asymmetrically  separated  (a),  and  in  those  of  the  third  to  symmet- 
rically linked  (s)  C-atoms,  and  so  on. 


Characterization  of  the  Ortho-,  Meta-,  and  Para-di- 
derivatives.     Determination  of  Position. 

1.  The  0-,  m-,  and  j9-compounds  are  characterized  by  their 
genetic  connection  witliin  each  particular  class. 


314 


BENZKNR  DERIVATIVES.     XVI.  SUMMARY. 


2.  The  amido-benzoic  acid  (M.  Pt.  145°),  which  has  already 
been  mentioned  on  p.  308  as  resulting  from  the  two  nitro- 
(meta-)  bromobenzoic  acids,  belongs  to  the  class  of  ortho- 
compounds,  and  the  amido-benzoic  acid  (M.  Pt.  174°),  also 
mentioned  there  as  prepared  from  the  two  nitro-  (ortho-)  oxy- 
benzoic  acids,  to  the  class  of  meta-compounds.  Consequently 
the  ortho-  and  the  meta-positions  are  those  which  are  found 
twice  in  the  molecule,  corresponding  to  the  notation  used  on 
p.  308  :  ab  =  af,  ac  =  ae.  Therefore  the  third  amido-benzoic 
acid  (M.  Pt.  187°),  which  is  isomeric  with  the  above  two 
others,  is  a  para-compound,  as  are  likewise  all  the  bi-deriva- 
tives  which  can  be  prepared  from  or  converted  into  it  by 
reactions  which  proceed  more  or  less  quantitatively,  ("glatt"). 
The  para-di- derivatives  are  thus  characterized  as  those,  the 
position  of  whose  substituents  (ad)  occurs  only  once  in  the 
benzene  molecule. 

3.  The  0-,  m-,  and  ^-compounds  allow  of  further  character- 
ization experimentally,  apart  altogether  from  theoretical  con- 
siderations. The  para-bi-derivatives  yield  always  only  one 
tri-derivative  when  a  third  H-atom  is  replaced  by  a  substituent, 
the  ortho-  yield  two,  while  the  meta-  yield  three  (CgHgRg  or 

Thus,  corresponding  to  one  of  the  di-bromo-benzenes,  CgH4Br2, 
(which  is  solid,  M.  Pt.  80°),  there  is  only  one  tri-bromo-benzene, 
CeHgBrg  ;  corresponding  to  another  (M.  Pt.  1°,  B.  Pt.  224°),  there  are 
two ;  and  corresponding  to  the  third  (liquid,  B.  Pt.  219°),  three 
dijfferent  tri-bromo-benzenes  {Korner).  The  same  holds  for  the  six 
nitro-dibromo-benzenes,  C6H3Br2(N02).  The  first  of  the  above  di- 
bromo-benzenes  is  a  para-,  the  second  an  ortho-,  and  the  third  a  meta- 
compound.  Precisely  analogous  relations  exist  between  the  three 
isomeric  di-amido-benzenes,  CgH4(NH2)2,  and  the  six  di-amido-benzoic 
acids,  C6H3(NH2)2(C02H),  derivable  from  them,  {Griess,  B.  7,  1223) ; 
between  the  three  xylenes,  C6H4(CH3)2,  and  the  six  nitro-xylenes, 
(Nolting,  B.  18, 2687);  and  between  the  three  phthalic  acids,  CgH4(C02H)2, 
and  the  six  oxy-phthalic  acids,  C6H3(OH)(C02H)2.  If  the  bi-derivatives 
which  yield  a  given  equal  number  of  tri-derivatives  be  tabulated 
together,  it  will  be  found  that  they  belong  in  every  case  to  one  and  the 
same  (o-,  m-,  p-)  class,  and  are  therefore  convertible  into  one  another. 

4.  The  close  agreement  between  the  facts  and  the  theory 


KEKULl^:'S  BKNZKNE  TITMORY. 


315 


^\\th  regard  to  the  existence  of  isomeric  di-  etc.  derivatives  has 
lent  a  wonderful  charm  to  the  endeavour  to  determine  which 
of  the  three  modes  of  linking,  1.2  (  =  1.6),  1.3  (  =  1.5)  and  1.4, 
indicates  the  ortho-,  which  the  meta-,  and  which  the  para-di- 
derivatives,  ("  determination  of  position  "). 

This  point  is,  in  the  first  instance,  easy  to  solve  in  the  case 
of  the  para-compounds.  The  C-atom  4  holds  a  position  of  its 
own  with  regard  to  C-atom  1,  i.e.  there  does  not  exist  a 
C-atom  which  is  linked  symmetrically  to  the  position  4,  1  ; 
consequently  the  para-compounds  are  1,  4  compounds. 

5.  Further,  it  is  seen  at  once  from  the  graphical  formula  of 
benzene  and  from  the  instances  just  to  be  given,  that  from  a 
1 : 4  di-derivative  only  one,  from  a  1 : 2  derivative  two,  and  from 
a  1 : 3  derivative  three  different  tri-derivatives  are  theoretically 
possible;  should  the  third  substituent  be  different  from  the 
two  first,  these  compounds  will  be  all  dissimilar,  but  should 
it  not,  then  they  will  be  in  part  identical : 


R 

R 
/\ 


R 


R 


\/ 


R 


R 


R 


R  R' 


R 


R 


R 
/\ 


R 


R 


R 


R 


R 


R 


R' 


The  para- derivatives  are  therefore  to  be  designated  as  1  : 4, 
the  meta-  as  1  :  3,  and  the  ortho-  as  1 :  2  compounds,  {Korner; 
see  Ladenburg's  memoir,  already  cited). 

6.  Other  arguments,  which  partly  forestalled  Korner^ s  proofs  in 
point  of  date,  have  led  to  the  same  result.  [Cf.  Ladenburg^s  proof 
of  the  equal  value  of  the  three  hydrogen  atoms  of  mesitylene,  already 
conjectured  by  Baeyer,  i.e.  of  the  symmetrical  nature  of  the  latter 
(  =  1:3:5),  from  which  the  position  1 :  3  follows  for  meta-xylene,  which 
can  be  prepared  from  it  (A.  179,  163)  ;  Grachevs  arguments  with 


316 


BENZENE  DERIVATIVES.     XVI.  SUMMARY. 


regard  to  the  constitution  1:2  of  ordinary  phthalic  acid,  on  account  of  its 
formation  by  the  oxidation  of  naphthalene  (A.  149,  22),  etc.,  etc.] 

7.  The  determination  of  position  of  the  tri-derivatives  depends  upon 
that  of  the  di-derivatives  which  can  be  transformed  into  the  former  or 
vice  versa.  If,  for  instance,  both  the  1  : 2  and  1  :  4  nitro-toluenes, 
CgH4(CIT3)(N02),  yield  one  and  the  same  di-nitro-toluene, 
C6H3(CH3)(N0.2)2»  on  the  introduction  of  a  second  nitro-group,  the 
methyl  in  the  latter  will  be  in  the  ortho-position  to  one  of  the  nitro- 
groups  and  in  the  para-position  to  the  other,  and  the  compound  will 
therefore  be  a  1  : 2 : 4  or  (a)  compound. 

Special  Benzene  formulae. 

The  graphical  benzene  formula  which  has  been  employed  up 
to  now  only  disposes,  however,  of  three  of  the  affinities  of  each 
carbon  atom.  The  fourth  affinities  serve,  according  to  KekuU, 
to  further  link  the  three  pairs  of  C-atoms  together,  so  that 
these  are  joined  alternately  by  single  and  double  bonds,  thus  : 


H 
G 


H 


This  formula  agrees  excellently  with  the  modes  of  formation 
of  benzene  and  trimethyl-benzene  from  acetylene  and  acetone 
(see  below),  with  its  relations  to  naphthalene  (p.  460),  and 
especially  with  the  capability — shown  both  by  benzene  and  by 
its  derivatives — of  forming  addition  compounds.  Combination 
with  H,  01,  etc.  thus  proceeds  here  exactly  as  in  the  case  of 
ethylene,  and  a  total  of  six  monovalent  atoms  can  be  taken  up. 

It  does  not,  however,  appear  self-evident  why  the  linking  1:2  should 
be  the  same  as  that  of  1:6,  since  the  two  neighbouring  C-atoms  are 
joined  in  the  former  case  by  a  single  bond  and  in  the  latter,  by  a  double 
one,  (cf.  Kekule,  A.  162,  86).  Besides  Kekule's  benzene  formula, 
many  others  have  been  proposed.  According  to  Claus  and  Korner 
the  0-atoms  1  and  4,  2  and  5,  and  3  and  6  may  be  linked  together  in  a 
quasi  diagonal  manner  (diagonal  formula  ;  this  does  not  explain  the 


SPECIAL  BENZENE  FORMULA. 


317 


existence  of  three  di-derivatives).  According  to  Dewar,  1  and  4  are 
linked  by  a  single  bond,  2  and  3,  and  5  and  6  by  double  ones.  Accord- 
ing to  Ladenburg,  there  are  only  single  bonds  between  1  and  4,  2  and  6, 
and  3  and  5  (prism  formula).  The  prism  formula  has  been  gone  into 
minutely  in  various  quarters  (see  e.g.  Ladenburg,  A.  172,  331 ;  also 
loc.  cit.),  but  Baeyer  criticises  it  as  not  meeting  the  necessities  of  the 
case  (B.  19,  1797). 

The  mode  in  which  the  C-atoms  are  linked  by  their  fourth  affinities 
very  probably  varies  according  to  the  nature  of  the  substituting  atomic 
groups.  The  question  of  the  constitution  of  the  benzene  derivatives  as 
a  whole  no  longer  exists  ;  the  present  task  of  investigators  lies  in 
endeavouring  to  explain  the  constitution  of  the  various  existing  typical 
groups  from  their  principal  representatives.  While  benzene  itself  may 
really  perhaps  possess  the  constitution  expressed  by  Kehule^s  graphical 
formula,  quinone,  for  instance,  is  a  derivative  of  a  dihydro-benzene  of 
the  formula  : 

-RG^     ^GH  HC<  >CH 

II         II  or  iVl 

HO         .CH  HC  /  ^CH 

^C^  ^C^ 

H2  Hg 

Certain  terpenes  probably  possess  a  **  para-bond,"  i.e.  have  the 
C-atoms  1  and  4  linked  diagonally  ;  such  formulae  would  correspond 
with  the  benzene  formula  of  Deioar  or  with  that  of  Koriitr  and  Glaus. 

The  benzene  nucleus  in  GqHq  is  designated  by  Baeyer  as  a 
"  tertiary/'  and  that  in  C^H^g?  hexamethylene,  as  a  "secondary" 
or  "  reduced  "  benzene  ring.  (See  Baeyer  on  the  constitution 
of  benzene,  A.  245,  103.) 


Laws  governing  substitution,  and  influence  of 
the  substituents  upon  one  another. 

1.  A  polyvalent  element  never  replaces  several  hydrogen 
atoms  together  in  a  single  benzene  nucleus ;  compounds  such 
as  GqHl^^O  and  CgH3=N  are  unknown. 

2.  In  the  formation  of  di-derivatives,  several  isomers  usually 
result  simultaneously,  one  of  them  generally  in  preponderating 
amount.  The  position  of  the  new  substituents  depends  upon 
that  of  those  already  present ;  thus  nitro-benzene  yields  chiefly 


318  BENZENE  DERIVATIVES.     XVI.  SUMMARY. 


m-nitro-chloro-benzene  when  chlorinated,  and  chloro-benzene 
chiefly  j>nitro-chloro-benzene  when  nitrated.  As  a  general 
rule,  when  CI,  Br,  I,  NO2  and  SO3H  enter  chloro-,  bromo-  or 
iodo-benzene,  phenol,  C^jH^.OH,  aniline,  CgH^.NHg,  or  toluene, 
CgHg.CHg,  it  is  always  the  para-compound  which  is  produced 
in  largest  quantity,  often  together  with  the  ortho-,  but  only 
in  rare  cases  with  the  meta-compound.  On  the  other  hand 
when  01,  Br,  I,  NOg  and  SO3H  enter  into  a  compound  which 
already  contains  NOg-,  SO3H-,  or  OOgH-,  they  almost  always 
take  up  the  meta-position  to  these  latter  groups. 

Through  the  entrance  of  (negative)  nitro-groups  or  of  halogen  atoms, 
the  acid  character  of  phenol  is  heightened,  while  the  basic  character 
of  amido-compounds  is  either  diminished  or  entirely  done  away  with. 
The  firm  linking  of  halogen  or  amidogen  in  the  benzene  nucleus  is  there- 
by loosened,  so  that  these  substituents  become  more  easily  exchangeable, 
e.g.  for  hydroxyl.  (Cf.  trinitro-chloro-benzene,  trinitro-phenol  and 
tri-nitraniline.) 

The  intensity  of  the  influence  in  question  is  dependent  upon  the 
position  of  the  newly-entering  substituent ;  thus  ortho-  and  para-chloro- 
(or  bromo-)  nitro -benzenes,  CgH4Cl(N02),  are  transformed  into  the 
corresponding  nitro-phenols,  C6H4(OH)(N02),  when  heated  with  a 
solution  of  potash  to  120°,  and  into  the  corresponding  nitranilines, 
C6H4(NH2)(N02),  with  ammonia  at  100°,  while  meta-chloro-  (or  bromo-) 
nitro-benzene  does  not  react  at  all.  In  an  analogous  manner,  o-dinitro- 
benzene  exchanges  a  nitro-group  for  hydroxyl  when  boiled  with  caustic 
soda  solution,  while  the  jp-  and  m-compounds  do  not. 

Further  Isomers  of  the  Benzene  derivatives. 

1.  The  isomerism  of  the  di-,  tri-,  etc.  derivatives,  "isomerism  of 
position  "  or  "  nucleus  isomerism,"  has  already  been  treated  of  on  pp. 
307  et  seq. 

2.  When  a  substituent  enters  the  benzene  nucleus  in  the  first 
instance  and  a  side  chain  (p.  325)  in  the  second,  the  so-called  "  mixed 
isomerism  "  is  the  result,  e.g.  : 

C6H4CI— CH3  and  CeHg— CH2CI ;  C6H4(CH3)2  and  C6H5(CH2.CH3). 
Mono-chloro-      Benzyl  chloride.     Xylene.  Ethyl-benzene, 
toluene. 

3.  When  the  side  chains  are  isomeric,  one  speaks  of  **side  chain 
isomerism,"  e.g.  : 

CgHg— CH2— CH2— CH3    and    CgHg— CH(CH3)2. 

Normal-  and  Iso-propyl-benzene. 


OCCURRENCE  OF  THE  BENZENE  DERIVATIVES.  319 


4.  Should  the  atoms  in  the  side  chains  (including  those  chains  which 
are  built  up  from  0,  S,  or  N)  be  unequally  divided,  '*  metamerism  "  in 
the  narrower  sense  of  the  word  results,  e.g.  : 

Salicylic  ethyl  ether.  Ethyl-salicylic  acid. 


Occurrence  of  the  Benzene  derivatives. 


Many  benzene  derivatives  occur  in  nature,  e.g.  oil  of  bitter 
almonds,  benzoic  acid  and  salicylic  acid,  while  others  result 
from  the  destructive  distillation  of  organic  substances,  especially 
of  coal. 

The  destructive  distillation  of  coal  yields  (a)  gases  (illumi- 
nating gas) ;  (b)  an  aqueous  distillate  containing  ammonium 
salts  etc.  ;  (c)  tar ;  and  (d)  coke. 

Coal  tar  contains : 

(a)  Fatty  hydrocarbons  in  small  amount. 

(6)  Aromatic  hydrocarbons,  the  most  important  of  which  are  the 
following  : 


Benzene, .  .  .  CgHg 
Toluene, .  .  .  CyHg 
0-,  m-,  and  p- 

Xylenes,  .  .  CgHjo 
Mesitylene,  .  .  C9H12 
Pseudo-cumene,  CgH^g 


Durene,  .  , 
Styrene,  .  . 
Naphthalene, 


CsHg 


Di-phenyl,  .  G12H10 
Acenaphthene,  C12H10 


Fluorene,  .  .  C13H10 
Anthracene,  .  C14H10 
Phenanthrene,  C14H10 


Pyrene,  . 
Chrysene, 


(c)  Other  neutral  bodies,  e,g,  alcohol  (in  very  small  quantity)  and 
carbazole,  C12H9N. 

(d)  Phenols,  e.g.  : 

Phenol  or  carbolic  acid,  CgHgO  ;  0-,  m-,  and  p-cresol,  CyHgO. 


Pyrrol,  .    .    .  C4H5N 
Pyridine,  .    .  C5H5N 
and  its  homologues. 


Aniline,    .    .  C6H7N 
Quinoline,     .  C9H7N 
and  its  homologues. 


Acridine, 


(See  SchultZy     Chemie  des  Steinkohlentheers,  '  Braunschweig,  1886. 
The  presence  of  the   hydrocarbons   CgHg,  C^Hg,  CgHj^ 
(m-  and  p-),  and  C^H^g  Ie3i8t  of  their  hydro- 


320  BENZENE  DERIVATIVES.     XVI.  SUMMARY. 


compounds,  has  recently  been  proved  in  most  natural 
petroleums,  American  petroleum  containing,  for  instance,  0.2 
p.c.  Cc)Hi2'  (cf-  P-  5^  ;  also  A.  234,  89  etc). 

Modes  of  formation  of  Benzene  derivatives. 

The  benzene  derivatives  can  only  be  produced  from  the 
fatty  compounds  by  a  relatively  small  number  of  reactions. 

1.  Many  methane  derivatives,  e.g.  alcohol,  yield  a  mixture 
containing  a  large  number  of  the  derivatives  of  benzene  when 
their  vapours  are  led  through  red-hot  tubes.  Acetylene,  C2H2, 
polymerizes  at  a  low  red  heat  to  benzene,  CgHg,  (Berthelot) : 

HC  CH  HC^  ^CH 

III  =  I  II 

HC  CH  HC^v  /CH 

In  an  analogous  manner  allylene,  C3H4,  =  CH3 — C=CH, 
yields  mesitylene,  CgH^g?  =  1:3:5  tri-methyl-benzene, 
CgH3(CH3)3,  when  distilled  with  dilute  sulphuric  acid,  while 
its  homologue  crotonylene,  C^Hg,  yields  hexa-methyl-benzene, 
CjgHig,  =  Cg(CH3)g ;  brom-acetylene  and  iod-acetylene  poly- 
merize to  tri-bromo-  and  tri-iodo-benzene  when  exposed  to 
light;  propargylic  acid,  C3H2O2,  polymerizes  to  trimesic  acid, 
CgHgOg,  and  so  on. 

2.  Ketones  condense  to  benzene  hydrocarbons  (p.  142)  when 
distilled  with  dilute  sulphuric  acid,  e.g,  acetone  yields  mesity- 
lene {Kanej  1838),  and  methyl-ethyl-ketone  tri-ethyl-benzene, 
etc.  : 

CH3  CH3 

(H2)CH  CH(H)2  yield 

CH3— C(0)         C(0)— CH3  CH3— C  C-CH3 

(H2)CH  H 
3  mols.  Acetone.  Mesitylene. 


MODES  OF  FORMATION. 


321 


*R0 

JOaR)— HC  i  H 


3.  Hexyl  iodide,  CgHjgl,  is  converted  into  hexa-chloro-benzene, 
CgClg,  by  heating  it  with  ICI3.  and  into  hexa-bromo-benzene,  CgBrg,  by 
bromine  at  260°  ;  the  latter  compound  can  also  be  obtained  by  heating 
CBr4  to  300°. 

4.  By  acting  with  sodium  upon  succino-di-ethyl  ether  {Herrmann^ 
A.  211,  306  ;  B.  16,  1411),  or  upon  brom-aceto-acetic  ether  (Buisberg), 
we  obtain  the  so-called  succino- succinic  ether"  (p.  430),  which  is  a 
**  diketo-hexamethylene-dicarboxylic  ether,"  and  is  easily  convertible 
into  dioxy-terephthalic  ether  and  hydroquinone  : 

CH,  «=  (CO.Il)— HC  CHo 

 ,  r     1      I  I 

HjCH— (CO2R)  >.  H2C  CH-(COjR) 

OR  ^CO^ 
2  mols.  Succino-di-ethyl  ether.  Succino-succinic  ether. 

*R  =  C2H5. 

5.  When  sodio-malonic-ether,  CHNa(C02R)2>  is  heated,  there  is 
formed  Phloroglucin-tricarboxylic  ether,  =  triketo-hexamethylene-tri- 
carboxylic  ether,  [Baeyer,  B.  18,  3454),  which  goes  into  phloroglucin 
on  saponification,  the  carboxyl  groups  being  broken  up,  thus  : 

(CO2R) 

CHiNa 


/ 


s 


•ROi.OC  CO;OR 


(CO2R)— HNaiC  CiNaiH— (CO2R) 

' \,  i  ■ 

:6r 


yields 


(CO2R) 

DC  CO 
I  I  +  3R0Na. 

(CO2R)— HC  CH-lCOaR) 

6.  Trimesic  ether  (B.  20,  2930)  results  from  the  condensation  of  3 
mols.  formyl-acetic  ether,  CHO — -CH^ — CO2R,  and  tri-acetyl-benzene, 
CgH3(CO.CH3)3,  in  an  analogous  manner  from  aceto-acetic  aldehyde, 
CH3— CO— CH2— CHO,  (B.  21,  1114). 

(500)  X 


322 


BENZENE  DERIVATIVES.     XVI.  SUMMARY. 


The  reactions  just  detailed  under  2,  5  and  6  depend  upon 
the  formation  of  a  benzene  nucleus  out  of  three  atomic  groups 
— CO — CHg — ,  with  elimination  of  3  mols.  HgO. 

7.  MeUitic  acid,  C6(C02H)g,  is  produced  by  the  oxidation  of  graphite 
or  lignite  by  means  of  KMn04. 

8.  Potassium  carboxide,  which  is  formed  by  the  action  of  carbonic 
oxide  upon  potassium,  is  the  potassium  compound  of  hex-oxy-benzene, 
C6(OH)6,  (see  p.  392). 

9.  Di-acetyl,  CH3— CO— CO— CHg,  goes  into  Xylo-quinone  (p.  394) 
under  the  influence  of  alkalies,  (B.  21,  1411.) 


The  converse  transformation  of  Benzene  derivatives 
into  Patty  compounds. 

1.  When  the  vapour  of  benzene  is  passed  through  a  red-hot 
tube,  it  is  partially  decomposed  into  acetylene. 

2.  Benzene  is  oxidized  by  chloric  acid  to  "  Trichloro-pheno- 
malic  acid,  i.e,  ^-trichlor-aceto-acrylic  acid,  CCI3.CO.CH : 
CH.CO2H,  {KeJcuU  and  Strecker,  A.  223,  170). 

When  chlorine  is  allowed  to  act  upon  phenol  in  alkaline  solution, 
the  benzene  ring  is  broken,  and  the  acids,  CgH5Cl304,  C6H5CIO4,  etc., 
are  produced,  {Hantzsch,  B.  20,  2780);  bromine,  acting  upon  bromanilic 
acid,  yields  perbromo-acetone,  CBrg — CO — CBrg. 

3.  Nitrous  acid  (NgO^)  converts  pyro-catechin  etc.  into 
dioxy-tartaric  acid. 

4.  Oxidizing  agents  which  are  capable  of  destroying  the 
benzene  ring  yield  carbonic,  formic  and  acetic  acids. 

5.  Hexa-hydro-benzene  is  transformed  into  hydrocarbons  of 
the  methane  series  when  treated  with  hydriodic  acid  at  280° 
(Berthelot).  This  decomposition  appears,  however,  to  be  very 
difficult  of  accomplishment. 


BENZENE  HYDROCARBONS. 


323 


XVII.  BENZENE  HYDROCARBONS. 
A.  Saturated  Hydrocarbons. 


Summary.-  [  ]  =  M.  Pt. ;  (  )  =  B.  Pt. 


^6^6 

CgHg,  Benzene  (80-5°). 

CyHg 

CgHglCHs),  Toluene  (111°). 

CeH,(CRs),,  Xylenes  (3) 
o-  =  (142°);  m-=(137°);2)-=(137°) 

C6H5(OH2.CH3),  Ethyl-benzene 
(134°). 

CeHgC  0113)3 
Trimethyl-benzenes  (3). 
s  =  Mesitylene  (163°). 
a  =  Pseudo-cumene  (169°) 
v=Hemellithene  (175°). 

06H4(OH3)(02H5) 

Methyl-ethyl- 
benzenes  (3) 
(e.g.  162°). 

^6^5(03117) 
Propyl-benzenes 

1.  Normal-propyl- 
(157°) 

2.  Iso-propyl- 

(  =  Oumene)(153°). 

C10H14 

^6112(0113)4 
Tetra-methyl- 

benzenes  (3): 
s=Durene 

[79°]  (190°). 
a=Iso-durene 

(195°). 
v=Prehnitene 

[-4°]  (204). 

^6113(0133)2(02115) 
Dimethyl- ethyl- 
benzenes 
(6  isomers 
possible). 

^6^14(02115)2 
Diethyl-benzenes 
(3). 

CeH,(CH3)(C3H,) 

Oymene 
(176°)  (6  isomers 

possible). 

^^6115(04119) 
Butyl- 
benzenes 
(4  possible) 
(167  -180°). 

06H(OH3)5,  Penta-methyl-benzene,  [51-5°]  (231°); 
CoH^iCQHii),  Amyl-benzene,  etc. 

C12H18 

06(CH3)6,  Hexa-methyl-benzene,  [164°]  (263°); 
06H3(02Hg)3,  Tri-ethyl-benzene,  etc. 

^14^22 

CqTL^{CqH.i>^),  Octyl-benzene,  etc. 

C6(C2H5)6,  Hex-ethyl-benzene  [126°]  (305°). 

324 


XVII.  BENZENE  HYDROCARBONS. 


The  benzene  hydrocarbons  are  for  the  most  part  colourless 
liquids  insoluble  in  water  but  readily  soluble  in  alcohol  and 
ether,  which  distil  without  decomposition;  (durene,  and 
penta-  and  hexa-methyl-benzenes  are  crystalline).  They 
possess  a  peculiar  and  sometimes  pleasant  ethereal  odour,  and 
burn  with  a  very  smoky  flame.  In  addition  to  benzene  itself, 
the  presence  has  been  proved  in  petroleum  of  its  methyl 
derivative  toluene,  the  three  xylenes,  the  three  tri-methyl- 
benzenes  and  durene. 

Modes  of  formation.  1.  By  treating  a  mixture  of  brominated 
hydrocarbon  and  iodo-  (or  bromo-)  alkyl  with  sodium  in  ethereal 
solution,  (the  Fittig  reaction,  A.  131,  303,  analogous  to  the 
Wurtz  reaction,  p.  38) : 

CeH^Br  -t-  CH3I  +  2Na  =  CgHs.CHg  +  Nal  +  NaBr ; 
C6H4Br(C,H5)  +  C2H5I  +  2Na  =  C6H4(C2H5)2  +  Nal  +  NaBr ; 
C6H4Br(CH3)  +C3H^I  +  2Na  =  C6H4(C3H^)(CH3)  +  Nal  +  NaBr 

2.  By  the  action  of  methyl  chloride  upon  benzene  or  its 
homologues  in  presence  of  aluminium  chloride,  {Gustavson,  the 
so-called    Friedel  and  Crafts'^  reaction) : 

CgHg  +  CH3CI    =  CgH^CHg     +  HCl 
CgHe  +  2CH3CI  =  C6H4(CH3)2  +  2HC1,  etc. 

This  reaction  is,  like  the  preceding  one,  capable  of  very  wide 
application ;  by  means  of  it  all  the  hydrogen  atoms  in  benzene 
can  be  gradually  replaced  by  methyl. 

Zinc  and  ferric  chlorides  act  in  the  same  way  as  chloride  of  alum- 
inium, while  ethyl  chloride  and  other  haloid  compounds,  such  as 
chloroform  and  acid  chlorides,  may  replace  methyl  chloride.  (See 
respectively  triphenyl-methane  and  the  ketones ;  cf  also  B.  14,  2624  ; 
B.  16,  1745  ;  Ann.  de  chim.  et  phys.  [6]  1,  419.) 

In  addition  to  this  synthetical  action,  aluminium  chloride  also  exerts 
a  breaking  up"  or  differentiating  action  on  the  homologues  of  benzene, 
e.g.  it  partly  transforms  toluene  into  benzene  and  xylene,  and  so  on, 
(B.  17,  2816  ;  18,  338  and  657).  Related  to  the  Friedel- Crafts  reaction 
is  the  Zincke  reaction  with  zinc  dust,  (see  diphenyl-methane). 

Alcohols  also,  like  their  haloid  ethers,  are  capable  of  reacting  in  an 
analogous  manner  in  presence  of  ZnClg : 

CfiHe  +  C4H9OH  =  C6H5.O4HC,  +  HgO. 


FORMATION  ;  CONSTITUTION. 


325 


3.  The  benzene  hydrocarbons  result  from  their  respective 
carboxylic  acids  by  the  splitting  off  of  the  carboxyl,  e.g.,  by 
distillation  with  soda-lime : 

CgH^C02H  =  C^jHg  +  ; 
CeH,(CH3)C02H  =  CeH5.CH3  +  CO^. 

4.  From  sulphonic  acids  (p.  37 4)  by  the  separation  of  the 
SOgH-group : 

CeH3(CH3),S03H  +  H^O  =  +  H,SO,. 

This  reaction  can  be  effected  by  dry  distillation,  by  heating  with 
concentrated  hydrochloric  acid  to  180°,  by  distillation  of  the  ammonium 
salt  {Caro),  or  by  treatment  with  superheated  steam,  e.g.,  in  presence 
of  some  concentrated  sulphuric  acid,  (Armstrong,  Kelhe.) 

5.  From  the  amido-compounds  by  transforming  these  into 
diazo-compounds  (p.  360),  and  boiling  the  latter  with  absolute 
alcohol  or  with  stannous  chloride. 

6.  By  distillation  of  the  phenols  (or  ketones)  with  zinc  dust. 

7.  For  synthesis,  see  above.  The  method  of  synthesis  for  paraffins, 
which  was  mentioned  on  p.  39,  is  also  occasionally  applicable  (see 
propyl-benzene). 

Isomers  and  Constitution.  The  table  given  on  p.  323  shows 
that  the  benzene  hydrocarbons,  from  CgH^Q  on,  exist  in  many 
isomeric  modifications ;  thus,  isomeric  with  the  three  xylenes 
we  have  ethyl-benzene,  with  the  three  tri-m ethyl-benzenes 
the  three  methyl-ethyl-benzenes  and  the  two  propyl-benzenes, 
with  durene,  cymene,  and  so  on. 

The  constitution  of  these  hydrocarbons  follows  very  simply 
from  their  modes  of  formation.  A  hydrocarbon  C^qH^^  for 
instance,  which  is  obtained  by  means  of  CH3CI  by  the  Friedel- 
Crafts  reaction,  can  only  be  a  tetra-methyl-benzene ;  another 
of  the  same  empirical  formula  C^qH^^,  which  has  been  prepared 
from  bromo-benzene,  butyl  bromide  and  sodium,  must  be  a 
butyl-benzene ;  while  a  third,  from  ^-bromo-toluene,  normal 
propyl  iodide  and  sodium,  must  be  a  ^-propyl-toluene 
(^-methyl-N-propyl-benzene),  etc.  The  synthesis  therefore 
determines  the  constitution. 

The  (carbon  containing)  groups  CH3,  CgHg,  etc.,  which 
replace  hydrogen  in  benzene,  are  termed  "  side  chains." 


326 


XVII.  BENZENE  HYDROCARBONS. 


According  to  the  number  of  side  chains  it  contains,  a 
benzene  hydrocarbon  is  converted  by  oxidation  into  a  benzene- 
mono-,  di-  or  tri-,  etc.,  carboxylic  acid,  e.g.  benzoic  acid, 
CgH^.COgH,  m-,  p-phthalic  acid,  G^^{GO^)^^  etc.  In  this 
way  a  further  means  is  afforded  of  determining  the  constitu- 
tion of  the  compounds  in  question. 

If,  for  example,  a  hydrocarbon  C9H12  yields  a  benzene-tri-carboxylic 
acid,  CgH3(C02H)3,  upon  oxidation,  it  must  contain  three  side  chains, 
i.e.,  must  be  a  tri -methyl-benzene  ;  should  a  phthalic  acid  on  the  other 
hand  result,  then  it  can  only  be  an  ethyl-toluene.  Since  cymene  yields 
p-  (or  tere-)  phthalic  acid,  C6H4(C02H)2,  in  oxidation,  its  two  side  chains 
must  be  in  the  ^-position  towards  one  another. 

The  respective  isomers  resemble  each  other  closely  in 
physical  properties,  their  boiling  points — for  example — lying 
very  near  together.  The  ortho-derivatives  often  boil  at  about 
5°  and  the  meta-  at  about  1°  higher  than  the  para-compounds; 
the  boiling  point  rises  with  an  increasing  number  of  methyl 
groups,  (cf.  p.  26). 

Behaviour.  1.  The  benzene  hydrocarbons  are  as  a  rule  easily 
nitrated  and  sulphurated,  mono-,  di-  and  even  tri-derivatives 
being  all  usually  capable  of  preparation,  according  to  the 
conditions.  It  is  only  the  H-atoms  of  the  benzene  nucleus 
which  enter  into  reaction  here,  in  accordance  with  the  theory 
which  regards  the  side  chains  as  paraffinic  residues,  as  which 
they  behave.  Hexa-methyl-benzene  can  thus  neither  be 
nitrated  nor  sulphurated. 

2.  Oxidation.  Benzene  can  only  be  oxidized  with  difficulty; 
permanganate  of  potash  converts  it  slowly  into  formic  and 
oxalic  acids,  some  benzoic  acid  and  phthalic  acid  being  produced 
at  the  same  time.  These  doubtless  result  from  some  previously 
formed  diphenyl. 

The  homologues  of  benzene,  on  the  other  hand,  are  readily 
oxidized  to  carboxylic  acids,  the  benzene  nucleus  remaining 
unaltered,  and  each  side  chain — no  matter  how  many  carbon 
atoms  it  may  contain — being  converted  as  a  rule  into  carboxyl. 

Nitric  acid  allows  of  a  successive  and  often  a  partial  oxidation  of 
individual  side  chains ;  chromic  acid  mixture  (KgCrgOy  -f  H2SO4)  acts 
more  energetically,  converting  all  the  side  chains  in  the  p-  and  m- 


Behaviour. 


327 


compounds  into  carboxyl,  and  completely  destroying  the  o-compounds. 
The  latter  may  be  oxidized  to  benzene-carboxylic  acids  by  KMn04  in 
the  cold. 

As  is  manifest  from  these  two  points,  the  homologues  of  benzene 
differ  somewhat  materially  from  benzene  itself ;  the  H-atoms  of  the 
side  chains  show  a  different  function  to  those  of  the  benzene  nucleus, 
the  former  behaving  like  the  hydrogen  atoms  in  a  paraffin.  It  thus 
follows  that  toluene  and  the  higher  homologues  may  be  derived  from 
methane  etc.  by  replacement  of  H  by  CgHg,  "phenyl,"  etc. 


3.  Eeduction.  As  mentioned  on  p.  312,  benzene  and  most 
of  its  derivatives  are  capable  of  taking  up  six  atoms  of 
hydrogen.  Benzene  itself  is  only  converted  into  hexa- 
hydro-benzene,  CgH^g,  with  difficulty,  but  toluene,  xylene 
and  mesitylene  combine  with  hydrogen  more  easily,  when 
they  are  heated  with  phosphonium  iodide,  PH4I,  to  a  rather 
high  temperature,  the  compounds  C^Hg.H2,  CgHj^.H^  and 
CgH^g-He  being  formed.  The  two  former  can  then  be  made 
to  take  up  more  hydrogen  by  energetic  reaction. 

Benzene  hydride  and  its  analogues  are  colourless  liquids  insoluble  in 
water  and  of  somewhat  lower  boiling  point  than  their  mother  com- 
pounds, into  which  they  can  be  readily  retransformed  by  oxidation, 
either  by  heating  with  sulphur  or  by  means  of  fuming  nitric  acid, 
nitration  also  taking  place  in  the  latter  case.  They  are  identical  with 
the     naphthenes  "  found  in  certain  varieties  of  petroleum. 

4.  Behaviour  with  halogens.  Chlorine  and  bromine  react 
differently,  according  to  the  conditions.  In  direct  sunlight 
they  yield  with  benzene  the  addition-products  CgHgClg  and 
CgH^jBrg,  while  in  diffused  daylight,  especially  in  presence  of 
a  little  iodine,  SbClg  or  M0CI5,  they  give  rise  to  the  substitu- 
tion products  CgH^Cl,  CgH^Br,  etc.  (For  further  details  see 
pp.  61  and  334.)  Those  hydrocarbons  which  do  not  contain 
their  full  complement  of  hydrogen  behave  exactly  like  un- 
saturated hydrocarbons,  in  so  far  that  they  are  capable  of 
taking  up  bromine  until  the  point  of  saturation,  C^X^^,  is 
reached,  (B.  21,  836). 

5.  Chromium  oxychloride,  CrOgCla,  converts  the  benzene  hydrocar- 
bons into  aromatic  aldehydes,  (p.  398). 


Cumene  or  phenyl-propane. 


328 


XVIL  BENZENE  HYDROCARBONS. 


The  numerous  *  condensations '  which  benzene  can  undergo 
with  oxygenated  compounds  in  presence  of  ZnClg,  ^2^5 
H2SO4,  and  with  chlorinated  compounds  in  presence  of  AlgClg, 
are  of  great  interest;  thus  benzene  yields  diphenyl-ethane  with 
aldehyde  and  sulphuric  acid,  and  benzophenone  with  benzoic 
acid  and  phosphorus  pentoxide. 

The  Hydrocarhon  OgHg. 

Benzene,  CgH^.  Discovered  by  Faraday  in  1825,  and 
detected  in  coal  tar  by  Hofmann  in  1845.  Benzene  is  obtained 
from  the  portion  of  coal  tar  which  boils  at  80-85°,  by  fraction- 
ating or  freezing.  It  may  be  prepared  chemically  pure  by 
distilling  a  mixture  of  benzoic  acid  and  lime.  The  ordinary 
benzene  of  commerce  usually  contains  thiophene  and  thus 
gives  the  indophenin  reaction,  but  it  may  be  freed  from  it  by 
repeated  shaking  up  with  small  quantities  of  sulphuric  acid. 
M.  Pt.  4° ;  B.  Pt.  80.5° ;  Sp.  Gr.  at  0°,  0.9.  It  burns  with 
a  luminous  smoky  flame  and  is  a  good  solvent  for  resins,  fats, 
iodine,  sulphur,  phosphorus,  etc.  When  its  vapour  is  led 
through  a  red-hot  tube,  diphenyl  is  obtained. 

Benzene  hexa-hydride,  CeHe-Hg.    B.  Pt.  69°.    Sp.  Gr.  at  0°,  0.76. 

Benzene  hexa-chloride,  OgHgClg,  is  produced  by  the  action  of  excess 
of  chlorine  on  benzene  in  sunlight.  It  is  a  solid  mass,  which  is  broken 
up  into  tri-chloro- benzene  and  hydrochloric  acid  on  distillation,  or  when 
treated  with  alkalies. 

Benzene  hexa-bromide,  CgHgBre.    M.  Pt.  212". 

The  Hydrocarbon  C^-Hg. 

Toluene,  C^Hg,  =  CeH^.CHg.  Discovered  in  1837.  For- 
mation :  by  the  dry  distillation  of  balsam  of  Tolu  and  of  many 
resins.  Synthesis  according  to  Fittig  (see  above).  Prepara- 
tion :  from  coal  tar,  in  which  it  is  found  accompanied  by  thio- 
tolene.  Toluene  is  very  similar  to  benzene.  It  boils  at  110°, 
and  is  still  liquid  at  — 28°.  Cr02Cl2  converts  it  into  benzoic 
aldehyde,  and  HNO3  or  CrOg  into  benzoic  acid. 


XYLENES,  ETC. 


329 


Toluene  di-hydride,  C^jHsiHaj.CHa,  and  -hexa-hydride,  CgHglHej.CHg, 
are  liquids  boiling  respectively  at  105- 108°  and  97°. 

Hydrocarbons,  CgHjo. 

{a)  m-,  andj^-Di-methyl-benzenes  or  Xylenes,  CgH4(CH3)2. 
The  xylene  of  coal  tar  consists  of  a  mixture  of  the  three 
isomers,  77i-xylene  being  present  to  the  extent  of  70  to  85  p.c. 
These  cannot  be  separated  from  one  another  by  fractional  dis- 
tillation. ??i-xylene  is  more  slowly  oxidized  by  dilute  nitric 
acid  than  its  isomers  and  can  thus  be  obtained  with  relative 
ease. 

For  the  separation  of  those  isomers  by  means  of  H2SO4,  see  B.  lO, 
1010,  14,  2625;  17,  444;  and  for  their  recognition  see  B.  19,  2513. 
Benzene  and  toluene  yield  chiefly  ortho-,  together  with  a  little  para- 
xylene,  when  subjected  to  the  Friedel- Grafts  synthesis,  (B.  14,  2627). 

1.  o-Xylene,  which  can  be  prepared  synthetically  from  o-bronio- 
toluene,  methyl  iodide  and  sodium,  is  oxidized  to  carbonic  acid  by  the 
chromic  acid  mixture,  and  to  o-toluic  acid,  C6H4(CH3)C02H,  by  dilute 
nitric  acid  ;  it  is  difficult  to  nitrate. 

2.  m-Xylene  or  Iso-xylene  also  results  from  mesitylene, 
CgH3(CHg)3,  1  :  3  :  5,  when  this  is  first  oxidized  to  mesitylenic 
acid,  CgH3(CH3)2C02H,  and  the  latter  then  distilled  with  lime. 
Dilute  nitric  acid  only  oxidizes  it  at  a  temperature  of  120°, 
while  chromic  acid  mixture  converts  it  into  iso-phthalic  acid, 
C6H4(C02H)2.  It  yields  a  Tetra-  and  Hexa-hydride,  CgH^^.H^ 
and  CgHiQ.Hg. 

3.  2^-Xylene.  Is  prepared  e.g.  from  ^-bromo-toluene  or,  better, 
p-dibromo-benzene,  methyl  iodide  and  sodium,  (B.  lO,  1356 ;  B.  17, 
444.)  M.  Pt.  15°.  Dilute  nitric  acid  oxidizes  it  to  ^-toluic  acid, 
C6H4(CH3)C02H,  and  terephthalic  acid,  C6H4(C02H)2. 

{h)  Ethylbenzene,  C6H5-C2H5.  Results  from  QHgBr  and  C2HgBr 
by  the  Fitlig  reaction,  from  styrene,  — C2H3,  and  HI,  and  from 
CgHg  and  C2H5CI  by  the  Friedel-G rafts  reaction.  Is  oxidized  to  benzoic 
acid. 

EydrocarhonSy  C^Hig,  (see  table). 
The  most  important  of  these  are  : 


330 


XVII.  BENZENE  HYDROCARBONS. 


(a)  Tri-methyl-benzenes. 

1.  Mesitylene,  1:3:  5-tri-methyl-benzene,  0^113(0113)3.  This 
is  contained  in  coal  tar  along  with  its  two  other  isomeric  tri- 
methyl-benzenes  ("  tar-cumene  " ),  and  can  be  prepared  from 
acetone  or  allylene  (p.  320).  It  is  a  liquid  of  agreeable  odour. 
Nitric  acid  oxidizes  the  side  chains  one  by  one,  while  chromic 
acid  mixture  decomposes  it  completely.  It  does  not  form  any 
isomeric  substitution  products  and  has  therefore  a  symmetrical 
constitution,  (Ladenburg,  A.  179,  160.) 

Mesitylene  hexa-hydride,  CgHig.He,  boils  at  138°. 

2.  Vsevido-cumenef  1 :2'A-tr{-methyl-benzene.  Present  in  coal  tar.  It 
is  separated  from  mesitylene,  not  by  fractional  distillation,  but  by 
taking  advantage  of  the  sparing  solubility  of  pseudo-cumene-sulphonic 
acid,  (B.  9,  258).  Its  constitution  follows  from  its  formation  from 
bromo-p-xylene,  1:4:2,  and  also  from  bromo-m-xylene,  1:3:4,  by  the 
Fittig  reaction.    Nitric  acid  oxidizes  the  side  chains  successively. 

3.  Hemellithene,  l:2:3-tri-methyl-benzene,  (see  B.  15,  1853).  Present 
in  coal  tar,  (B.  20,  903). 

(b)  Ethyl-toluenes,  C6H4(CH3)(C2H5).  The  m-  and  ^-compounds  are 
known. 

(c)  Propyl-benzenes,  CgH^ — CgH^.  These  are  oxidized  to 
benzoic  acid. 

1.  N-Propyl-benzene,  CgHg — CHg — CHg — CH3,  results  from  bromo- 
benzene  and  normal  propyl  iodide  by  the  Fittig  reaction,  and  also  from 
benzyl  chloride,  CgHg.  CH2CI,  and  zinc  ethyl. 

2.  Iso-propyl-benzene  or  Cumene,  CgH^ — CH=(CIl3)2,  is 
produced  by  the  distillation  of  cumic  acid,  CgH4(C3lI^)(C02H), 
with  lime ;  from  benzene  and  iso-  or  normal  propyl  iodide  by 
means  of  AlgCl^,  in  the  latter  case  with  molecular  rearrange- 
ment (p.  65) ;  and  from  benzylidine  chloride,  CgHg — CHClg, 
and  zinc  methyl,  this  last  method  furnishing  proof  of  its  con- 
stitution. 

For  the  transformation  of  the  normal-  into  the  iso-propyl  group  in 
cumene  and  cymene  derivatives,  see  B.  18,  Ref.  152. 

Hydrocarbons^  CiqHj^.    (See  table.) 
Among  these  may  be  mentioned 


UNSATURATED  BENZENE  HYDROCARBONS.  331 


Durene,  1:2:4:5-  or  s-tetra-methyl-benzene,  C(3H2(CH3)4,  which 
has  recently  been  found  in  coal  tar  and  can  be  prepared  from 
toluene  and  methyl  chloride  by  the  Friedel-Crafts  reaction,  or 
from  dibromo-m-xylene  (from  coal  tar  xylene),  methyl  iodide 
and  sodium,  (A.  216,  200).  It  is  a  solid,  M.  Pt.  79°,  and 
possesses  a  camphor-like  odour.  For  its  constitution,  see  B. 
11,  31.    Both  of  its  isomers  are  known  (see  table). 

Methyl-propyl-benzenes,  CgH4(CH3)C3H^.  The  most  impor- 
tant of  these  is  cymene  or  p-methyl-N-propyl-benzene.  It  is  found 
in  Eoman  cummin  oil  (Cuminum  cyminum),  and  results  upon 
heating  camphor  with  PgS^  or,  better,  PgO^,  also  by  heating 
oil  of  turpentine  with  iodine,  etc.  It  has  been  synthetically 
built  up  from  ^-bromo-toluene,  N-propyl  iodide  and  sodium. 
It  is  a  liquid  of  agreeable  odour,  and  yields  either  j9-toluic, 
terephthalic  or  cumic  acid  upon  oxidation,  according  to  the 
conditions. 

Isomeric  with  the  above  are  the  Butyl-benzenes,  C6H5(C4H9),  of  which 
three  are  known. 

Hydrocarhon,  O^gH^g. 

Hexa-methyl-benzene,  melUteney  C6(CH3)g,  crystallizes  in  prisms  or 
plates  which  melt  at  169°.  It  can  neither  be  sulphurated  nor  nitrated, 
(see  p.  326).    KMn04  oxidizes  it  to  mellitic  acid,  C6(C02H)6. 

For  the  higher  homologues  see  table,  p.  323. 

B.  Unsaturated  Benzene  hydrocarbons. 

The  benzene  hydrocarbons  containing  less  hydrogen  comport 
themselves  on  the  one  hand  like  benzene  itself,  and  on  the 
other  like  the  unsaturated  hydrocarbons  of  the  fatty  series, 
combining  readily  with  hydrogen,  halogen,  halogen  hydride, 
etc.  They  are  derived  from  the  olefines  or  acetylenes  by  the 
exchange  of  H  for  CgH^,  thus :  (CgIl5)CH=CH2,  styrene  or 
phenyl-ethylene ;  {CqH.^)G=GR,  phenyl-acetylene. 

styrene,  CeHg.CH^CHg,  occurs  along  with  other  compounds  in 
storax  (styrax  officinalis),  and  in  the  juice  of  the  bark  of  Liquidambar 
orientale.  It  results  upon  heating  cinnamic  acid  (p.  417)  with  water  to 
200°: 


332  XVIII.  HALOID  SUBSTITUTION  PRODUCTS. 


CfiHg— CH-CH— COoH  =  CgHg— CH=CH2  +  CO2. 

For  its  preparation  see  A.  195,  131.  Styrene  is  a  liquid  like  benzene 
and  of  agreeable  odour.  B.  Pt.  146°.  It  changes  on  keeping  into  the 
polymeric  meta-styrene,  an  amorphous  transparent  mass,  and  goes  into 
ethyl-benzene  when  heated  with  hydriodic  acid.  Addition  of  HBr 
converts  it  into  a-bromo-ethyl-benzene,  CgHg — CHg — CHgBr. 

Phenyl-acetylene,  CeHg.C^CH,  is  produced  e.g.  by  the  separation  of 
CO2  from  phenyl-propiolic  acid  (p.  419) : 

CeHg-CEEC— CO2H  =   CeHg— C=CH  +  COg. 

It  is  a  pleasant  smelling  liquid  boiling  at  139°,  and  gives  proof  of  its 
being  an  acetylene  derivative  by  yielding  white  and  pale  yellow 
explosive  metallic  compounds  with  solutions  of  silver  and  cuprous 
oxides.  It  combines  with  water  to  aceto-phenone,  CgHg.CO.CHg,  when 
it  is  dissolved  in  sulphuric  acid  and  the  solution  is  diluted  with  water. 


XVIII.  HALOID  SUBSTITUTION  PRODUCTS. 

Summary, 

The  numbers  in  the  square  brackets  [...]  indicate  melting,  and  those  in 
the  round  ones  (...)  boiling  points. 


CeH^Cl 
Chloro-benzene  (133°). 
C6H4CI2 
Di-chloro-benzenes 
0-  :  (179°)  ;  m-  :  (172°) ; 
p- :  [56°],  (173°). 


CeH^Br 
Bromo-benzene  (154°). 

Di-bromo-benzenes 
0- :  (224°) ;  m-  :  (219°) ; 
p-  :  [89°],  (219°). 


lodo-benzene  (185°). 

Di-iodo-benzenes 
(e.g.,  285°). 


CeHgCls,  (3),  Tri-chloro-benzenes  (208°  to  218°). 

C6H2GI4,  (3),  Tetra-chloro-benzenes. 

CetlClg,  (1),  Penta-chloro-benzene. 

CgCle,      (1),  Hexa-chloro-benzene  [226°],  (332°). 


CeH4Cl(CH3) 

^^6^6  CH2CI 

(3)  Chloro-toluenes  (156°-160°). 

Benzyl  chloride  (179°). 

115^12(^113) 

^6^5 — CHCI2 

(6)  Di-chloro-toluenes  (e.g.,  196°). 

Benzal  chloride  (206°). 

etc. 

^6^5 — CCI3 

Benzo-tri-chloride  (213°). 

C6H3C1(CH3)2,  (6)  Chloro-xylenes. 

C6H4(CH3)(CH2C1),  Xylyl  chlorides. 

C6H4(CH2Br)2,  (3)  Xylylene  bromides,  etc., 


HALOID  SUBSTITUTION  PRODUCTS. 


333 


Haloid  substitution  products  in  immense  number  are  derived 
from  the  benzene  hydrocarbons  by  the  exchange  of  hydrogen 
for  halogen.  They  are  either  colourless  mobile  liquids  or 
crystalline  solids,  insoluble  in  water  but  readily  soluble  in 
alcohol  and  ether,  which  distil  unchanged,  and  are  distinguished 
by  their  peculiar  odour  and  also,  in  part,  by  their  irritant 
action  upon  the  mucous  membrane.  They  are  heavier  than 
water. 

The  substitution  products  of  benzene  itself  and  those  of  its 
homologues  have  to  be  distinguished  from  one  another.  In 
the  former  the  halogen  is  bound  very  firmly,  far  more  so  than 
in  methyl  chloride,  ethyl  iodide,  etc. ;  it  cannot  be  exchanged 
for  OH  (through  AgOH),  or  for  NHg  (through  NH3),  etc., 
sodium  almost  alone  being  capable  of  bringing  it  into  reaction, 
(see  the  Fittig  reaction^  p.  324). 

The  substitution  products  of  toluene,  etc.,  on  the  other 
hand,  do  not  all  show  a  similar  behaviour.  Some  of  them, 
e,g.,  chloro-toluene,  contain  the  halogen  bound  very  fast,  while 
in  others  of  them,  e.g.,  benzyl  chloride,  the  halogen  atoms 
enter  into  reaction  as  readily  as  do  those  of  the  haloid  sub- 
stitution products  of  the  methane  series.  After  oxidation, 
which  transforms  all  the  side  chains  into  carboxyl  (p.  326), 
the  halogen  remains  in  the  former  compounds,  with  formation 
of  chlorinated,  etc.,  benzoic  acids,  e.g.,  CgH^Cl — COgH,  but  it 
is  eliminated  in  the  latter,  benzyl  chloride  e.g.  giving  benzoic 
acid,  CgHg — COgH.  From  this  it  follows  that  the  halogen  is 
present  in  the  one  case  in  the  benzene  nucleus,  and  in  the 
other  in  the  side  chain. 

This  is  in  accordance  with  the  conclusion  arrived  at  on  p.  327,  of 
toluene  being  phenylated  methane;  chloro-toluene,  C6H4C1.(CH3),  is 
quasi-methylated  chloro-benzene  and  is  therefore  stable,  while  benzyl 
chloride,  CgHg— CHgCl,  is  quasi-phenylated  chloro-methyl,  and  is 
therefore  very  active  chemically. 

The  same  relations  repeat  themselves  in  xylene  and  the  other 
homologues  of  toluene,  so  that  it  is  always  easy  to  arrive  ?t  the  con- 
stitution of  a  compound  from  the  behaviour  of  its  halogen  atoms  .and 
from  its  products  of  oxidation.  Thus  a  compound  CyH/^l^,  which 
yields  mono-chloro-benzoic  acid  upon  oxidation,  has  manifestly  the 
formula  CgH^Cl— CHgCl  (chloro-benzyl  chloride). 


334 


XVIII.  HALOID  SUBSTITUTION  PRODUCTS. 


For  the  capability  of  reaction  of  the  chlorinated  benzenes,  cf.  also 
p.  318. 

The  boiling  points  of  the  (position-)  isomeric  substitution  products 
(o-,  m-f  and  p-compounds),  always  lie  near  to  one  another,  and  those  of 
the  other  isomers  also  are  not  very  far  apart  from  these. 

Modes  of  formation,  1.  By  the  action  of  chlorine  or  bromine 
upon  aromatic  hydrocarbons  there  result,  according  to  the 
conditions,  either  addition  or  substitution  products,  the  latter 
class  particularly  easily  in  presence  of  iodine.  (Cf.  p.  327, 
also  B.  18,  607.)  Iodine  only  substitutes  directly  under  the 
conditions  already  detailed  at  p.  61.  From  benzene  all  the 
chlorinated  derivatives  up  to  CgClg  can  be  obtained  in  succession, 
the  last  named  compound  resulting  with  the  aid  of  MoCl^,  ICI3, 
etc.,  at  a  somewhat  high  temperature.  A  hexa-bromo-benzene 
also  exists,  but  not  a  hexa-iodo-compound.  In  the  case  of 
toluene  and  its  homologues  the  halogen  enters  the  benzene 
nucleus  alone,  if  the  operation  is  performed  in  the  cold,  with 
the  exclusion  of  direct  sunlight  or  with  the  addition  of  iodine ; 
while,  if  its  vapour  is  led  into  the  boiling  hydrocarbon,  or  if 
the  experiment  is  conducted  in  sunlight  and  without  addition 
of  iodine,  it  goes  almost  exclusively  into  the  side  chain, 
(Beilstein;  Schramm;  see  also  B.  13,  1216). 

2.  From  compounds  containing  oxygen  (the  phenols,  aromatic 
alcohols,  aldehydes,  ketones,  and  acids),  by  the  action  of  phos- 
phorus pentachloride  or  bromide  : 

CgH^.OH  +  PCI5  =  CgH^Cl  +  POCI3  +  HCl. 

3.  From  the  (nitro-  or)  primary  amido-compounds,  these 
being  first  converted  into  diazo-compounds  (p.  360).  Upon 
boiling  the  latter  with  cuprous  chloride  or  bromide,  they  are 
transformed  into  the  corresponding  chlorine  or  bromine  com- 
pounds {Sandmeyer,  B.  17,  1633,  2<">50)  and  upon  boiling  with 
iodide  of  potassium,  i^tvj  iodo-substitution  products : 

OoH,.N=N.Cl  =  CgH^Cl  +  N2; 
CgH,.N=N.Cl  +  KI  =  CgH.I  +  N2  +  KCI. 

The  bromine  compounds  also  result  upon  boiling  the  diazo-per- 
bromides  (p.  304)  witli  absolute  alcohol,  and  the  fluorine  compounds  by 
a  similar  reaction,  (  Wallachy  A.  236,  255). 


CHLORO-  AND  BROMO-BENZENES,  ETC. 


336 


4.  By  heating  the  haloid-substitution  acids  with  lime ; 

CgH^Cl-COaH  ^  C,B,Cl  +  H,0. 


Mono-chloro-,  bromo-,  and  iodo-benzene  are  colourless  liquids 
of  peculiar  odour.  Their  boiling  points  have  been  given  in  the 
summary. 

Di-chloro-  and  Di-bromo -benzenes  exist  as  o-,  m-,  and  ^j-compounds. 
The  p-,  and  also  the  o-compounds  in  smaller  amount,  are  obtained 
directly  (see  p.  318),  while  the  m-compounds  are  obtained  indirectly 
from  m-dinitro-benzene  according  to  method  3,  The  para-compounds 
are  solid  and  the  others  liquid. 

The  significance  of  the  di-  and  tri-bromo-benzenes  for  the  benzene 
theory  has  been  already  indicated  at  p.  314.  The  tri-chloro-benzene 
which  results  by  direct  substitution  has  the  (asymmetric)  constitution 
1:2:4.    It  may  also  be  formed  by  the  separation  of  3HC1  from  CgHg.Clg. 

Hexa-chloro-  and  -bromo-benzenes  are  produced  by  the  thorough 
chlorination  or  bromination  of  benzene,  toluene,  naphthalene,  etc.,  and 
also  from  carbon  tetrachloride  and  bromide,  as  given  at  p.  321.  They 
are  solid  and  can  be  distilled. 

Fluo-benzene,  CqH^Y,  is  a  liquid  boiling  at  85°;  the  entrance  of 
fluorine  into  the  benzene  molecule  thus  alters  its  boiling  point  only  in 
slight  degree. 

Mono-chloro-  and  -bromo-toluenes,  CgH^C^CHg)  and 
CgH4Br(CH3).  These  mono-substitution  products  of  toluene 
likewise  exist  as  di-derivatives  of  benzene  in  the  o-,  m-,  and 
^-modifications. 

When  toluene  is  chlorinated  or  brominated,  as  given  on  p.  334, 
the  para-  and  ortho-compounds  are  formed  in  approximately  equal 
quantities.  m-Chloro -toluene  is  obtained  from  chloro-^-toluidine, 
C6H3.C1(NH2)CH3  (from  ^^-toluidine  and  CI),  according  to  method  3. 
The  ^-compounds  are  solid  in  the  cold  and  the  others  liquid.  Oxidation 
by  HNO3,  Cr03  or  KMn04  converts  them  into  the  haloid-benzoic  acids, 
but  chromic  acid  mixture  must  only  be  used  in  the  case  of  the  p-  and 
m-f  and  not  in  that  of  the  o-compounds,  as  it  completely  disintegrates 
the  latter. 

Benzyl  chloride,  CgH^— CHgCl  (Cannizaro),  results  upon 
chlorinating  boiling  toluene,  and  benzyl  bromide  in  an 
analogous  manner;  the  latter  can  be  converted  into  benzyl 
iodide  by  iodide  of  potassium.  The  behaviour  of  these  com- 
pounds shows  them  to  be  the  haloid  ethers  of  benzyl  alcohol, 


336  XIX.  NITRO-SUBSTITUTION  PRODUCTS. 


C^^Hg — CHg.OH,  from  which  they  result  by  the  action  of 
halogen  hydride,  and  into  which  they  are  transformed  by 
prolonged  boiling  with  water  or,  better,  with  a  solution  of 
carbonate  of  potash.  Boiling  with  potassium  acetate  yields 
the  acetic  ether  of  this  alcohol,  with  potassium  sulph-hydrate 
the  mercaptan,  and  with  ammonia  the  amine  base. 

They  are  colourless  liquids,  heavier  than  water,  which  boil 
without  decomposition  and,  like  o-bromo-toluene,  etc.,  irritate 
the  mucous  membrane  of  the  nose  and  eyes  exceedingly. 
Oxidation  converts  them  into  benzoic  acid.  Benzyl  chloride 
is  used  on  the  large  scale  for  the  preparation  of  oil  of  bitter 
almonds  and  for  modifying  the  tints  of  dyes. 

Benzal  chloride,  benzylidene  chloride,  CgH^ — CHClg,  and 
Benzene  tri-chloride,  C^H^ — CCI3,  are  produced  by  the  further 
chlorination  of  boiling  toluene  and  also  by  the  action  of  PCI5 
upon  the  corresponding  oxygen  compounds,  benzoic  aldehyde, 
CgHg — CHO,  benzoic  acid,  CgH^ — CO2H,  and  benzoyl  chloride, 
CgHg — COOL  They  are  liquids  resembling  benzyl  chloride, 
and  are  reconverted  into  the  original  oxygen  compounds  by 
superheating  with  water,  and  into  benzoic  acid  by  oxidizing 
agents.  For  their  relations  to  cinnamic  acid  and  malachite 
green,  see  these. 

CMoro-bromo-benzenes,  C6H4ClBr,  Cblor-iodo-benzenes  and  other 
mixed  derivatives  also  exist  in  large  number. 

Substitution  compounds  of  unsaturated  hydrocarbons  are  likewise 
known,  e.g.  jS-Bromo-styrene,  CgHg — CBr=CH2,  a-Bromo-styrene, 
CgHg— CH=CHBr,  etc.,  etc. 

XIX.  NITRO-SUBSTITUTION  PRODUCTS  OF 
THE  AROMATIC  HYDROCARBONS. 

When  benzene  derivatives  (not  merely  hydrocarbons)  are 
treated  with  concentrated  nitric  acid,  most  of  them  are  easily 
dissolved,  with  evolution  of  heat,  and  transformed  into  nitro- 
compounds which  are  precipitated  on  the  addition  of  water. 
According  to  the  conditions  of  the  experiment  and  the  nature 
of  the  compound  to  be  nitrated,  one  or  more  nitro-groups  enter 


NITRO  COMPOUNDS  ;  PROPERTIES. 


337 


the  molecule  (see  e.g,  phenol).  The  iiitro-groups  substitute  in 
the  nucleus  and  only  very  seldom  in  the  side  chain. 

Summary, 


C,^,m,)  CeH^iNO^)^  CeH3(N03)3 

Nitro-benzene.         o-,  m-,  and  ^^-Dinitro-  s-Trinitro-benzene. 

Liq.    B.  Pt.  206°.  benzenes.  Solid.    M.  Pt.  121°. 

Solid.    M.  Pts.  118°,  90°, 
and  171°. 


0;  m-,p-Nitro-toluenes. 
B.Pts.223°,230°and238° 
7?-compound  solid. 


CeH3(CH8)(N02)2 
Dinitro-tolaeues. 


C6H3(CH3),N02 
Nitro-xylenes. 
e.g.  1:3:4,  (CH3  in  1) 
Liq.    B.  Pt.  238°. 


CeH^CllN-O^) 
Nitro-chloro-benzenes. 

etc. 


C6Pl2(CH3)3N02,  etc. 
Nitro-mesitylene. 
Solid.    M.  Pt.  42^ 
B.Pt.  255°.. 


CeBr^lNO^)^ 
Tetrabromo-dinitr  0- 
benzene. 


Nitro-compounds  are  also  produced  by  the  action  of  nitrous  acid  upon 
diazo-compounds,  in  the  presence  of  cuprous  oxide,  {Sandmeyer,  B.  20, 
1414) : 

CgHg— Nr=:]Sr— CI  +  NHO2  =  CgHg-NOs  +  HCl  +  N2. 
Diazo-benzene  chloride.  Nitro-benzene. 

The  nitro-compounds  are  for  the  most  part  pale  yellow 
liquids  which  distil  unchanged  and  volatilize  with  water 
vapour,  or  colourless  or  pale  yellow  needles  or  prisms  ;  some- 
times they  are  also  of  an  intensive  yellow  or  red  colour. 
Many  of  them  explode  upon  being  heated.  They  are  heavier 
than  water  and  insoluble  in  it,  but  most  of  them  are  readily 
soluble  in  alcohol,  ether  and  glacial  acetic  acid. 

The  nitro-group  in  most  aromatic  nitro-compounds  is  bound 
very  firmly,  as  in  the  case  of  the  nitro-methanes,  and  is  not 
exchangeable  for  other  groups.  Like  the  latter  compounds 
also,  they  are  easily  reduced  in  acid  solution  to  the  correspond- 
ing amido-derivatives  ;  in  alkaline  solution  they  are  converted 
into  azoxy-,  azo-  and  hydrazo-compounds,  (see  pp.  366  and 
367). 

(606)  '  Y 


338  XIX.  NITRO-SUBSTITUTION  PRODUCTS. 


On  the  other  hand,  they  cannot  be  prepared  according  to  mode  of 
formation  1  for  nitro-methane  (p.  101),  i.e.  by  the  action  of  AgNOg  on 
CgHgCl  etc. 


Nitro-benzene,  C6H5(N02),  {Mitscherlich,  1834).  Eesults, 
with  evolution  of  heat,  on  the  gradual  addition  of  benzene  to 
fuming  nitric  acid,  or  on  treating  it  with  a  mixture  of  sulphuric 
and  the  calculated  quantity  of  nitric  acid.  It  is  a  yellowish 
liquid  with  an  intensive  odour  of  oil  of  bitter  almonds,  which 
solidifies  in  the  cold  ;  M.  Pt.  +  3°- 

Dinitro-benzenes,  CgH4(N02)2.  These  are  produced  when 
benzene  is  boiled  with  fuming  nitric  acid;  in  this,  as  in  all 
analogous  cases,  the  two  nitro-groups  take  up  the  meta-position 
to  one  another,  very  little  of  the  o-  and  j9-compounds  being 
formed,  and,  by  recrystallizing  from  alcohol,  pure  m-dinitro- 
benzene  is  obtained  in  long  colourless  prisms  or  needles. 

The  o-compound  crystallizes  in  tables  and  the  ^-compound 
in  needles,  both  being  colourless ;  they  are  prepared  indirectly 
by  elimination  of  NH2  from  the  corresponding  di-nitranilines. 

Upon  reduction  there  result  first  the  three  nitranilines  and 
then  the  phenylene-diamines  (pp.  352  and  359). 

o-Nitro -benzene  exchanges  a  nitro-group  for  hydroxyl  when  boiled 
with  caustic  soda,  and  for  amidogen  when  acted  on  by  ammonia,  with 
the  formation  of  o-nitro-phenol,  C6H4(N02)(OH)  and  o-nitraniline, 
C(jH4(N02)(NH2)-  The  m-compound  is  oxidizable  by  KgFeCyg  to  a-  and 
/3-dinitro-phenol. 

Nitro-toluenes,  CgH4(CH3)(N02).  When  toluene  is  nitrated, 
the  ;p-  and  o-compounds,  with  hardly  any  of  the  m-compound, 
result.  The  first  is  solid,  crystallizing  in  large  prisms,  and 
the  second  liquid,  the  latter  being  used  as  a  perfume  under 
the  name  of  "oil  of  mirbane.''  m-Nitro-toluene  can  be  prepared 
indirectly  from  m  nitro-^-toluidine,  CgH3(CH3)  (N02)(NH2), 
by  the  Griess  reaction  (p.  363). 

Further  nitration  gives  rise  to  : 

Dinitro-toluenes,  C6H3(CH3)(N02)2,  of  the  constitution  CHgiNOgiNOg 
=  1:2:4  and  1:2:6,  the  two  nitro-groups  being  again  in  the  m-position 
to  one  another  in  both  cases.    (Cf.  p.  316.) 


NITRO-  AND  NITROSO-COMPOUNDS. 


339 


Most  of  these  nitro-compounds  are  of  great  technical 
importance,  on  account  of  their  convertibility  into  amine 
bases. 

Chloro-  and  Bromo-nitro- benzenes. 

When  chloro-  or  bromo-benzene  is  nitrated,  p-chloro-  (or  bromo-) 
nitro-benzenes,  and  in  smaller  quantity  the  o-compounds,  result.  The 
m-compounds  must  be  prepared  indirectly  by  replacing  an  amido-group 
in  m-nitraniline  by  halogen.  The  ^-derivatives  have  a  higher  melting 
point  than  their  isomers,  and  the  m-compounds  for  the  most  part  a 
higher  one  than  the  o -derivatives,  this  IsiW  frequently  repeating  itself 
in  other  cases  also.  The  ^^-derivatives  are  usually  also  less  soluble  in 
alcohol.  The  o-  and  p -compounds,  but  not  the  m-,  exchange  halogen 
for  hydroxyl  when  boiled  with  potash,  and  for  amidogen  when  heated 
with  ammonia. 

In  Trinitro-chloro-lbenzene,  C6H2(N02)3C1,  the  chlorine  atom  has 
been  rendered  so  easily  exchangeable  by  the  acidifying  influence  of  the 
nitro-groups  that  the  compound  behaves  as  an  acid  chloride  ;  hence  the 
name  "  picryl  chloride,"  the  chloride  of  picric  acid  (p.  318). 

Nitro-xylenes,  -mesitylene  and  -pseudo- cumene  are  also  known  in 
many  isomeric  modifications,  (see  table). 

We  are  further  acquainted  with  nitro -derivatives  of  styrene,  viz.,  o-, 
m-,  and  p -Nitro- sty renes,  C6H4(N02)(C2H3),  which  can  be  prepared  by 
indirect  methods,  and  also  a -Nitro -styrene,  C6H5CH=CH(N02),  which 
results  directly  from  the  nitration  of  styrene  and  contains  the  nitro- 
group  in  the  side  chain,  a  necessary  consequence  of  its  preparation  from 
benzoic  aldehyde  and  nitro-methane  by  means  of  zinc  chloride,  thus  : 
C^Hg.CHO  +  CH3NO2  =  C(jH5.CH=CH(N02)  +  H2O. 

This  is  one  of  those  relatively  rare  cases  in  which  the  nitro-group 
enters  the  side  chain  upon  direct  nitration.  (Cf.  B.  18,  935,  2438 ; 
19,  836.) 

Nitroso-derivatives  of  the  Hydrocarbons. 

There  exist  but  few  aromatic  nitroso-compounds,  i.e.  substances 
which  contain  the  nitroso-group,  NO,  in  place  of  a  benzene  hydrogen 
atom. 

Nitroso -"benzene,  C5H5(NO),  is  produced  by  the  action  of  NO. CI  upon 
mercury  di-phenyl  dissolved  in  benzene.*  It  is  only  known  mixed 
with  benzene ;  the  mixture  is  a  green  liquid  of  sharp  smell,  which 
yields  aniline  when  treated  with  tin  and  hydrochloric  acid,  and 
azo-benzene  with  aniline  acetate. 

*  Mercury  di-phenyl,  Hg(C(.H5)2,  is  an  analogue  of  mercury  di-ethyl ; 
it  results  from  the  action  of  mercury  upon  mono-bromo-benzene,  and 
crystallizes  in  needles  or  prisms  melting  at  120°. 


340 


XX.  AMIDO-COMPOUNDS. 


Nitroso-derivatives  of  tertiary  amines  result  directly  by  the  action 
of  nitrous  acid  upon  the  latter.  (See  Nitroso-dimethyl-aniline, 
C6H4(NO)N(CH3)2,  p.  354.) 

XX.  AMIDO-DERIVATIVES  OP  THE 
BENZENE  HYDROCARBONS. 

(See  table,  p.  341). 

Aniline,  the  simplest  of  the  aromatic  bases,  may  be  regarded 
(1)  as  benzene  in  which  a  hydrogen  atom  is  replaced  by 
amidogen,  amido-benzene "),  or  (2)  as  ammonia  in  which 
a  hydrogen  atom  is  replaced  by  phenyl,  OgH^ — ,  (^'phenyl- 
amine").  According  to  the  former  view,  amido-compounds 
are  derived  from  all  the  benzene  hydrocarbons,  and  not  only 
monamines  (containing  NHg),  but  also  di-amines  (2NH2), 
tri-amines,  etc. ;  according  to  the  latter,  the  phenyl  group 
may  enter  anew  with  the  formation  of  secondary  or  tertiary 
amines.  Secondary  and  tertiary  amines,  and  even  quaternary 
ammonium  compounds  may  also  result  from  the  entrance  of 
alcohol  radicles  into  the  above  monamines,  diamines,  etc. 

NHg,  etc.,  may  likewise  substitute  in  the  side  chain. 

An  extraordinarily  large  number  of  aromatic  bases  are  thus 
theoretically  possible  and  also  actually  known  (see  table). 
They  closely  resemble  in  some  ways  the  nitrogen  bases  of  the 
alcohol  radicles,  form  salts  with  acids — frequently  with  evolu- 
tion of  heat — and  double  salts  with  chloride  of  platinum, 
possess  a  basic  odour,  give  rise  to  white  clouds  with  volatile 
acids,  and  distil  for  the  most  part  unchanged,  etc.  Speaking 
generally,  however,  they  are  weaker  bases  than  the  alcoholic 
amines,  since  the  phenyl  group,  CgH^,  possesses  a  negative 
character,  and  not — like  the  alcohol  radicles — a  positive; 
thus  the  salts  of  diphenylamine  are  decomposed  even 
by  water,  and  triphenylamine  no  longer  possesses  basic  pro- 
perties, while  dimethyl-aniline  has  a  strongly  marked  basic 
character. 

[Continued  on  p,  342. 


AMIDO-COMPOUNDS. 


341 


Summary, 


Primary. 

Secondary. 

Tertiary. 

1                                            ■    MONAMINES.  1 

Aniline 
[-8°]  (183°). 

(CeH,),,NH 
Diphenylamine 

[54°]  (302^^). 

Trlphenylamine 
[127']. 

C«H4(CH3)NH2 
Toluidines. 
0-  :     m-  :       p- : 
(199°),  (197°),  [45°]  (198°). 

C6H3(CH3)2NH2 
(6)  Xylidines,(e.r7.  217°). 

C6H2(CH3)3NH2 
Pseudo-cumidine  [62°]. 

C6H4(N0,)NH2 
NitrodiilinGS, 
0-  :     m-  :        p-  : 
[71°]  [114°]  [147°]  (285°). 

CeH5(CH2.NH2) 
Benzylamine  (183°). 

C6H5(CH2.CH2.NH2) 
Phenyl-ethylamine 
\          (193°),  etc. 

Alhylat 

CeH5.NH.CH3 
Methyl-aniline  (192°). 

C6H5.NH.C2H5 
Ethyl-aniline  (204°). 

Nitroso-{ 

(CA)2N.N0 
Nitroso-diphenylamine 
[66°] 

Acid  D 

C6H5.]SrH(C2H30) 
Acetanilide  [114°]. 

CO.(NHC6H5)2 
Carbanilide  [235°]. 

CS(NHC6H5)(NH,) 
Phenyl-thio-urea  [154°] 
etc. 

ed  Bases. 

C6H5.N'(CH3)2 
Dimethyl-aniline  (192°). 

C6H5.N(CoH5)2 

Diethyl-aniline  (213°). 

ierivatives. 

CeH,(N0).F(CH3), 
Nitroso-dimethyl-aniline 
[85°] 

erivatives, 

Methyl-acetanilide  [99°]. 

COCN.QHg) 
Phenyl  cyanate  (163°). 

CS(N.CeH,) 
Phenyl-isothiocyanate 
(222°)  etc. 

1               Diamines,  etc. 

/  C6H4(NH2)2, 
Phenylene-diamines, 
(o-i   [102°]  (252°) 
\  m- :  [63°]  (287°) 
[p-:  [1471(267°). 

C,H3(CH3)(NH2)2 
Toluylene-diamines 
e.g.  1:2:4  [99°]  (286°). 

C6H4(NH2)[N(CH3)2]  Amido-dimethyl-aniline, 
p-  ;  [4r]  (257°). 

C6H4(NH2)(NH.  CgHg)  Amido-dipheny lamine, 
p- :  [66°]. 

■^^'\C6H4'nH2  P-^iamido-dipheny lamine  [158°]. 

NH[C6H4.  N(CH3)2]2  75-TetramethyI-diamido- 
diphenylamine. 

Triamido-benzenes. 
\  Tetramido-benzene. 

342 


XX.  AMIDO-COMPOUNDS. 


The  diamines  have  a  more  strongly  basic  character  than  the 
monamines  and  are  more  readily  soluble  in  water. 

A.  Primary  Monamines. 

Isomers.  The  isomerism  of  the  aromatic  is  in  part  analogous  to  that 
of  the  fatty  amines  (p.  113),  e.g.,  dimethyl-aniline  is  isomeric  with  the 
methyl-toluidines  and  the  xylidines.  Cases  of  isomerism  are  also  caused 
by  the  amido-group  being  present  in  the  benzene  nucleus  in  the  one  case 
and  in  the  side  chain  in  the  other.  Finally  all  the  isomeric  relations 
of  the  aromatic  hydrocarbons  (bi-derivatives,  etc.)  may  also  come  into 
play  here. 

Constitution.  As  already  seen  at  pp.  114  et  seq.,  amines  are  very 
easy  to  characterize  as  primary,  secondary,  etc.  Not  only  their 
modes  of  formation  but  also  their  behaviour  shows  whether  the  amido- 
group  is  present  in  the  benzene  nucleus  or  in  the  side  chain. 

Modes  of  formation.  1.  The  most  important  mode  of  pre- 
paration of  the  primary  aromatic  bases,  and  also  of  the  di-amines, 
etc.,  consists  in  the  reduction  of  the  nitro-compounds  : 

CeHj.NO^  +  STL,  =  2Rp  +  CeH^.NH^ 

Nitro-benzene.  Aniline. 

CeH,(N0,)2  +         =  AR,0  +  CJi.m,), 

V  >   ^ 

Y  T 

Di-nitro-benzenes.  Phenylene -diamines. 

The  reduction  of  nitro-  to  amido-compounds  goes  on  espe- 
cially well  in  an  acid  solution,  e.g.,  by  the  gradual  addition  of 
the  latter  to  a  warm  mixture  of  tin  or  stannous  chloride  and 
hydrochloric  acid.  On  a  manufacturing  scale  iron  and  a 
limited  amount  of  hydrochloric  acid  are  used  (Bechamp),  also 
frequently  zinc  dust  and  hydrochloric  or  acetic  acid.  Am- 
monium sulphide  (Zinin),  ferrous  sulphate  and  baryta  water, 
etc.,  also  effect  the  reduction. 

Sulphide  of  ammonium  acts  more  mildly  than  tin  and  hydrochloric 
acid  and  is  therefore  of  special  value  for  the  partial  reduction  of  dinitro- 
compounds  (see  nitraniline).  An  alcoholic  solution  of  stannous  chloride 
containing  hydrochloric  acid  may  also  be  used  for  this  purpose,  (B.  19, 
2161). 

Amines  also  result  from  the  reduction  of  nitroso-compounds,  (see 
nitroso-dimethyl-aniline. ) 


PRIMARY  AMINES  ;  FORMATION. 


343 


2.  By  heating  phenols  with  the  compound  of  zinc  chloride  and 
ammonia,  or  of  calcium  chloride  and  ammonia,  to  300°  (Tl/erz),  secondary 
amines  being  formed  at  the  same  time  : 

CeHg.OH  +  HNH2  =  CgHg.NHa  +  H^O. 

This  reaction  goes  on  more  easily  in  the  presence  of  negative  groups, 
e.g.  with  the  nitro-phenols,  (B.  19,  1749). 

3.  By  distilling  amido-acids  with  lime,  sometimes  by  merely  heating 
them  alone  : 

C6H4(NH2)C02H  =  C6H5.NH2  +  CO2. 

4.  By  heating  secondary  and  tertiary  bases  (such  as  mono- 
and  dimethyl-aniline),  which  have  been  formed  by  the  intro- 
duction of  the  alcohol  radicle  into  primary  aromatic  bases, 
with  strong  hydrochloric  acid  to  180°,  the  alcoholic  radicle  can 
be  eliminated  again  in  the  form  of  alkyl  chloride  with  repro- 
duction of  the  primary  bases  : 

C6H5.N(CH3)2  +  2HC1  =  CeH5,NH2  +  2CH3CI. 

If  the  temperature  is  raised  higher,  the  separated  CH3CI  (i.e. 
chloro-alkyl)  acts  further  upon  the  primary  amine,  causing  the  replace- 
ment of  hydrogen  of  the  benzene  nucleus  by  alcoholic  radicle  and  the 
consequent  formation  of  primary  bases  which  are  homologous  with  the 
original  amine ;  in  this  way  toluidine  hydrochloride  results  upon 
heating  hydrochloride  of  methyl-aniline  to  335° : 

C^Hg.NHCCHg),  HCl  =  CgHg.NHs  +  CH3CI  =  C6H4(CH3)NH2,  HCl. 

The  methyl  groups  which  thus  enter  the  nucleus  take  up  the  0-  or 
p-,  and  not  the  w,-position,  to  the  regenerated  NHg. 

In  an  analogous  manner  one  finally  obtains  from  trimethyl-phenyl-am- 
monium  iodide,  0(^115. N(CH3)3l,  mesidine  hydriodide,  €2112(0113)3. NHg, 
HI.    Hydrochloride  of  diphenylamine  does  not  show  this  reaction. 

4^.  The  formation  of  {e.g. )  amido-isobutyl-benzene,  by  heating  aniline 
hydrochloride  with  isobutyl  alcohol  to  250°,  depends  upon  the  same 
principle,  thus  : 

C6H5.NH2,  HCl  +  C4H9OH  =  C6H4(C4H9).NH2,  HCl  +  H2O. 

5.  For  the  formation  of  amido-compounds  from  nitro-haloid-benzenes 
or  o-dinitro-benzenes,  see  p.  339. 

6.  By  heating  the  potassium  salts  of  sulphonic  acids  with  sodio- 
amide,  NaNH2,  (B.  19,  902). 

7.  The  aromatic  amines  cannot  be  obtained  by  heating 
chloro-benzene,  etc.  with  ammonia  (see  p.  333).  Benzylamine, 
however,  and  all  analogously  constituted  bases,  which  contain 


3U 


XX.  A]\rrDO-COMPOUNDS. 


the  NH2-group  in  the  side  chain,  result  by  the  methods  which 
apply  in  the  preparation  of  amines  of  the  fatty  series.  Thus 
benzylamine  is  formed  by  the  action  of  ammonia  or,  better, 
of  acetamide  upon  benzyl  chloride  (the  latter  method  giving, 
rise,  of  course,  to  the  readily  saponifiable  acetyl-benzylamine), 
by  reduction  of  benzaldehyde-hydrazone  (p.  373  ;  B.  19,  1924), 
etc.  The  above  also  holds  good  for  secondary  and  tertiary 
bases  of  this  kind. 

Properties.  The  primary  monamines  are  partly  liquid,  partly 
solid  and  beautifully  crystallizing  bases.  They  are  colourless 
when  pure,  but  readily  become  brown  when  exposed  to  the 
air,  and  possess  a  weakly  basic  and  not  disagreeable  odour. 
Aniline  is  somewhat  soluble  in  water  (1  :  31),  its  homologues 
less  so. 

Behaviour,  1.  Most  of  them  yield  with  acids  salts  which 
crystallize  well  and  which  are  usually  readily  soluble  in  water. 
They  do  not  however  unite  with  very  weak  acids,  such  as 
carbonic,  and  they  are  therefore  separated  from  their  salts  in 
the  free  state  by  sodium  carbonate.  Sodium  acetate  often  acts 
in  the  same  way  (when  no  acetates  exist).  They  yield  double 
compounds  with  many  metallic  salts,  especially  with  platinic 
chloride  [e.g.  2(C6H^N,HC1)  +  PtClJ,  and  with  gold  chloride; 
also  with  stannous  and  zinc  chlorides,  etc.  The  platinum 
double  salts  are  often  sparingly  soluble  and  therefore  suited 
for  the  isolation  of  the  bases. 

Besides  these  there  exist  the  so-called  addition  salts  of  those  bases, 
e.g.  aniline' zinc  chloride,  2C6H7N  +  ZnClg,  aniline  mercuric  chloride, 
2C(iH7N  +  HgClg,  and  so  on. 

2.  When  aniline  is  heated  with  potassium  or  sodium,  the  hydrogen 
is  replaced  by  metal  with  formation  of  the  compounds  CgHgNHK  and 
CgHgNKg.  These  yield  di-  and  triphenylamine  with  bromo-benzene, 
and  decompose  immediately  with  water. 

3.  For  behaviour  with  sulphuric  and  nitric  acids  and 
with  halogens,  see  pp.  352  and  375. 

4.  The  primary  aromatic  bases  are  analogous  in  every 
respect  to  the  primary  fatty  ones,  methyl  iodide,  benzyl 
chloride  etc.  transforming  them  into  secondary,  tertiary  and 
quaternary  compounds  : 


PRIMARY  AMINES  ;  BEHAVIOUR. 


345 


C.Hg.NH.,  +  CH3I  =  C„H,.NH(CH3),  HI ; 
CeH5.NH(CH3)  +  CH3I  =  C„H,.N(CH3)2,  HI ; 
CeH5.N(CH3)2  +  CH3I  =  C«H,.N(CH3)3l. 

The  secondary  and  tertiary  bases  can  be  liberated  from  their 
hydriodides  by  soda,  but  moist  oxide  of  silver  must  be  used  in 
the  case  of  the  ammonium  bases,  (see  p.  115). 

5.  Aldehydes  react  with  the  primary  bases,  with  elimination  of 
water,  thus  : 

CH3.CHO  +  2C(5H5.NH2  =  CH3.CH(NH.C6H5)2  +  HgO. 

Ethylidene-diphenyl-diamine. 

Benzoic  aldehyde,  however,  reacts  as  follows  : 

C6H5.CHO  +  NH2.C6H5  =  CgHs.CH-N— CgHg  +  HgO. 

 ^ — ,  

Benzylidine-aniline. 

6.  Just  as  acids  yield  ,  amides  with  ammonia,  so  are  they 
capable  of  forming  '^anilides"  with  aniline,  etc.,  e.g,  acetic 
acid  and  aniline  give  acetanilide  : 

C6H5.NH2  +  C2H3O.OH  =  C6H5.NH(C2H30)  +  H2O. 

These  anilides  may  either  be  looked  upon  as  acetylated 
etc.  amines  or  as  phenylated  etc.  amides,  the  formula 
C2H30.NH(C(3H5)  corresponding  with  the  latter  view.  They 
are  in  every  respect  analogous  in  their  chemical  behaviour 
to  the  ordinary  amides,  especially  to  the  alkylated  amides 
(p.  180),  being  broken  up  again  into  their  components  by 
alkalies,  and  resulting  by  analogous  methods,  e.g.  by  heating 
the  acid  or,  better,  its  anhydride  or  chloride  with  the  amine  in 
question,  thus  : 

C,H4(CH3)NH2  +  CH3.C0C1  =  C6H4(CH3).NH.C2H30  +  HCl. 

Toluidine.  Acet-toiuide. 

7.  When  warmed  with  chloroform  and  alcoholic  potash,  the 
primary  bases,  like  those  of  the  fatty  series,  yield  iso-nitriles 
of  stupefying  odour.  When  they  are  warmed  with  carbon 
bisulphide  thio-ureas  result,  and  from  the  latter  iso-thiocyan- 
ates,  e.g,  on  treatment  with  phosphoric  acid,  (cf.  pp.  Ill  and 
276). 


346 


XX.  AMIDO-COMPOUNDS. 


8.  Nitrous  acid  converts  the  primary  aromatic  amines  in  acid 
solution  into  diazo-compounds  (p.  360),  and  in  the  absence  of 
acids  into  diazo-amido-compounds  (p.  364).  The  diazo-com- 
pounds go  into  phenols  when  boiled  with  water,  so  that  NHg  is  here 
indirectly  exchangeable  for  OH,  as  is  the  case  directly  with  the  amines 
of  the  fatty  series.  When  the  amines  are  warmed  with  ethyl  nitrite  in 
alcoholic  solution,  the  amido  group  is  eliminated,  i.e.  replaced  by 
hydrogen  (p.  362). 

9.  The  oxidation  products  of  the  primary  bases  are  very 
various,  phenols,  quinones,  azo-compounds,  aniline  black,  etc., 
resulting  according  to  the  conditions;  a  mixture  of  aniline 
and  toluidine  yields  fuchsine. 

10.  The  bases  which  contain  the  amide  in  the  side  chain 
possess,  in  contradistinction  to  the  purely  aromatic  amines,  the 
character  of  the  amines  of  the  fatty  series.  They  are  thus  e.g. 
not  convertible  into  diazo-compounds. 

B.  Secondary  Monamines. 

We  have  to  distinguish  here  between  purely  aromatic 
secondary  amines,  such  as  diphenylamine,  and  mixed  secondary 
bases  which  contain  an  aromatic  residue  and  a  radicle  of  the 
fatty  series. 

Modes  of  formation.  1.  Mixed  secondary  bases  result  from 
the  primary  by  treatment  with  methyl  iodide,  etc.  (Hofmann), 
(see  p.  112). 

This  reaction  does  not  usually  stop  short  with  the  introduction  of  one 
alcoholic  radicle,  but  extends  further  with  the  formation  of  tertiary 
bases.  In  order  to  avoid  this,  the  alkyl  iodide  etc.  may  be  allowed  to 
act  upon  the  acetylated  primary  bases,  e.g.  acetanilide  [or  upon  their 
sodium  compounds  {Hepp),]  and  the  resulting  acetyl  compound  be 
saponified  : 

C6H5.]SrH(C.,H30)  +  CH3I  =  C6Hg.N(CH3)(C2H30)  +  HI. 

The  secondary  bases  are  separated  from  the  tertiary  by  treatment 
with  nitrous  acid  (see  below,  under  Nitrosamines). 

2.  The  purely  aromatic  secondary  amines  result  upon  heat- 
ing the  primary  bases  with  their  hydrochloric  acid  salts  : 


SECONDARY  MONAMINES. 


347 


CgH^.NHH  +  CeH^.NH^HCl  =  ^^c^s^nh,  HCl  +  NH3. 

Unsymmetrical"  bases  (i.e.  those  containing  two  different  radicles) 
have  also  been  prepared  in  this  way. 

3.  Diphenylamine  can  further  be  got  by  heating  phenol  with  aniline 
zinc  chloride,  (B.  17,  2632),  and  : 

4.  By  the  action  of  bromo-benzeile  upon  potassium-aniline. 

Behaviour.  1.  The  mixed  secondary  bases  have  strongly 
marked  basic  properties,  while  the  purel}^  aromatic  have  not, 
(cf.  p.  340). 

2.  For  the  breaking  up  of  the  mixed  bases  by  hydrochloric  acid,  see 
p.  343. 

3.  The  hydrogen  of  the  imido-groiip  is  replaceable  by  an 
alcoholic  or  acid  radicle,  and  also  by  potassium  or  sodium  : 

(CeH5),NH  +  CH3I      =  HI  +  (CeH5)2N(CH3) 

Methyl-diphenylamine. 

(CeH,)2NH  +  (C2H30),0  =  C,H,0,  +  (0^11^(0^130) 

Acetyl-diphenylamine. 

4.  The  secondary  bases  give  neither  the  iso-nitrile  nor  the 
"mustard  oil"  reaction  (p.  114). 

5.  With  nitrous  acid,  nitrosamines  are  formed,  (cf.  p.  115): 

CeH5NH(CH3)  +  NO.OH  =  H^O  +  C6H5.N(NO).(CH3) 

^  ,  ^ 

Nitroso -methyl-aniline. 

These  Nitrosamines  are  neutral  oily  liquids  insoluble  in 
water,  which  regenerate  the  secondary  bases  when  heated 
with  stannous  chloride  or  with  alcohol  and  hydrochloric  acid, 
and  which  yield  hydrazines  with  mild  reducing  agents. 

They  serve  for  preparing  the  secondary  bases  pure,  since  they  alone 
are  precipitated  by  sodium  nitrite  as  non-basic  oils  from  the  acid 
solution  of  a  mixture  of  primary,  secondary  and  tertiary  bases.  When 
such  nitrosamines  are  digested  with  alcoholic  hydrochloric  acid,  a 
molecular  rearrangement  takes  place  and  compounds  of  the  nature 
of  nitroso-dimethyl-aniline  (p.  318)  are  formed,  the  nitroso-group  going 
into  the  nucJeus,  (0.  Fischer  and  Hepp,  B,  19,  2991)  : 

CeHg— N(N0)-CH3  =  C6H4(NO)-NH.CH3. 


348 


XX.  AMIDO-COMPOUNDS. 


0.  Tertiary  Monamines. 

These  also  are  either  purely  aromatic  or  mixed  (fatty- 
aromatic)  bases. 

Modes  of  formation.  1.  The  latter  result  upon  alkylating 
the  primary  or  secondary  bases  (cf.  p.  345),  which,  however, 
may  be  heated  with  methyl  alcohol  and  hydrochloric  acid 
instead  of  methyl  chloride  or  iodide. 

2.  Tri-phenylamine,  a  purely  aromatic  base,  is  formed  by  the  action 
of  bromo-benzene  upon  di-potassium-aniline  : 

CeHgNKg  +  2C6H5Br  =  [Q.TL,)^^  +  2KBr. 

Behaviour,  1.  Unlike  the  mixed  (fatty-aromatic)  amines, 
the  purely  aromatic  tertiary  amines  are  incapable  of  forming 
salts. 

2.  They  do  not  yield  iso-nitriles  with  CHCI3,  iso-thiocyanates 
with  CSg,  or  acid  derivatives  with  acid  chlorides,  but  they  do 
yield  quaternary  compounds  with  methyl  iodide. 

3.  Nitrous  acid  acts  upon  the  tertiary  aromatic  bases  (which 
thereby  differ  from  the  tertiary  bases  of  the  fatty  series)  with 
the  formation  of  nitroso-compounds  which  contain  the  NO- 
group  linked  to  the  benzene  nucleus  : 

CeH,.N.(CH3)2  +  NO.OH  =  G,11^(^0).^{GR^\  +  H^O. 

V  ^  ^  ^ 

Nitroso-  dimethyl-  aniline. 

Such  nitroso-derivatives  are,  in  contradistinction  to  the 
nitrosamines  already  mentioned,  changed  into  amido-com- 
pounds  (di-amines)  by  reduction,  (see  below). 

D.  The  Quaternary  Bases 

C3]'respond  entirely  with  the  quaternary  bases  of  the  fatty  series. 
Trimethyl-phenyl-ammonium  hydroxide,  CgH5.N( 0113)3.  OH,  for  in- 
stance, is  a  colourless,  strongly  alkaline,  bitter  substance  which  breaks 
up  into  dimethyl-aniline  and  methyl  alcohol  when  heated.  Some  of 
the  tertiary  amines  hLwever  are  not  capable  of  yielding  ammonium 
compounds. 


DIAMINES  AND  TRIAMINES. 


349 


E.  Di-amines,  Tri-amines,  etc. 

Formation.  1.  By  the  reduction  of  the  dinitro-hydrocarbons 
or  of  the  nitro-amido-compounds.  In  this  way  the  phenylene- 
diamines,  CgH4(NH2)2,  result  from  the  dinitro-benzenes  (see 
table,  p.  341.)  The  o-  and  ^-diamines  are  best  obtained  from 
the  0-  and  j?-nitro-amido-compdunds  (p.  352). 

2.  Further,  a  new  amido-group  can  be  introduced  in  the  p-position  into 
a  monamine,  especially  a  secondary  or  tertiary  such  as  C  gHg — N(CH3)2, 
by  first  transforming  the  latter  into  an  azo-dye  (e.g.  benzene-azo- 
dimethyl-aniline,  p.  371)  hy  uniting  it  with  diazo-benzene  chloride, 
and  decomposing  this  by  reduction  (p.  370). 

Tri-amido  compounds  can  be  prepared  in  a  manner  exactly  analogous. 

3.  For  the  preparation  of  di-amines  from  nitroso-compounds  of 
tertiary  amines,  see  amido-dimethyl-aniline,  C6H4(NH2)[N(CH3)2]. 

4.  Tetr-amido-benzene,  C6H2(NH2)4,  is  formed  by  nitrating  (pre- 
viously acetylated)  di-amido-benzene,  and  reducing  the  resulting 
dinitro-compound,  the  two  acetyl  groups  being  finally  split  off,  (B.  20, 
328). 

Behaviour.  The  diamines  and  triamines  are  solid  compounds 
which  crystallize  in  tables  or  plates  and  distil  unchanged. 
They  are  soluble  in  water,  especially  upon  warming.  Though 
originally  without  colour,  most  of  them  quickly  become  brown 
in  the  air,  their  instability  increasing  with  the  number  of 
amido-groups  present.  In  accordance  with  the  readiness  with 
which  they  are  oxidized,  they  frequently  yield  characteristic 
colourations  with  ferric  chloride,  e.g,  o-phenylene-diamine  a 
dark  red,  and  1:2: 3-tri-amido-benzene  a  violet  and  then  a 
brown  colour. 

The  three  isomeric  varieties  of  diamines  differ  materially  in  their 
behaviour  : 

(a)  Ortho- diamines.  1.  Ferric  chloride  yields  a  crystalline  precipi- 
tate of  yellow-red  needles  with  a  solution  of  o-phenylene-diamine. 

2.  The  acid  derivatives  of  the  o-compounds  change  into  compounds 
of  the  nature  of  amidines,  the  so-called  "  anhydro-bases,"  through  the 
formation  of  intramolecular  anhydride  ;  thus,  by  the  reduction  of  o-nitr- 
acetanilide  by  tin  and  hydrochloric  acid,  there  results  *'phenylene- 

ethenyl-amidine,"  a  derivative  of  ethenyl-amidine,  CHg— C^^^  (A. 

209,  339)  : 


350 


XX.  AMIDO-COMPOtJNDS. 


C6H4<Nor^°'^^'  +  3H,-2H,0  =  C.H^gH-CO.CH, 
=  C6H4<^>C-CH3  +  H,0. 

Compounds  of  this  nature  are  also  obtained  by  heating  o-diamines 
with  acids. 

3.  A  similar  reaction  takes  place  between  aldehydes  and  diamine 
hydrochlorides,  with  the  formation  of  the  so-called  aldehydine  bases," 
HOI  being  set  free,  {Ladenburg,  B.  11,  590;  19,  2025).  In  the  same 
way  glyoxal,  CHO — CHO,  yields  quinoxaline,  and  many  of  the  double 
ketones  react  analogously.  With  CSNH,  isothiocyanates  are  formed, 
(A.  221,  1). 

4.  Nitrous  acid  converts  the  o-diamines  into  the  so-called  *'azimido- 
compounds,"  compounds  which  contain  three  atoms  of  nitrogen,  e.g. 
o-phenylene-diamine   into    azimido- benzene,   =  amido-azo-phenylene, 

^6H4<^>N  (B.  9,  214,  1524;  15,  1878,  2195;  19,  1757). 

(6)  Meta-diamido-bases.  1.  These  form  yellow-brown  dyes  with 
nitrous  acid,  even  when  only  traces  of  the  latter  are  present  (see  azo- 
colouring  matters). 

2.  They  yield  azo-dyes  with  diazo-benzene  chloride  (see  chrysoidin). 

3.  With  nitroso-dimethyl-aniline,  or  on  oxidation  together  with 
para-diamines,  blue  colouring  matters  are  obtained,  and,  upon  boiling, 
red  (see  toluylene  red). 

4.  With  CNSH,  phenylene-di-ureas  are  formed  (A.  221,  1). 

(c)  Para-diamido-compounds.  1.  When  warmed  with  FcgClg  or, 
better,  with  MnOg  +  H2SO4,  quinone,  C6H4O2  (or  a  homologue),  results 
and  may  be  recognized  by  its  odour. 

2,  All  p-diamines  which  contain  a  primary  NHg-group  yield  violet 
or  blue  colouring  matters  containing  sulphur  and  belonging  to  the  thio- 
diphenylamine  group  (p.  356),  when  'Fe^Clg  is  added  to  their  dilute 
acid  solution  containing  sulphuretted  hydrogen. 


Aniline, 

Aniline,  amido-benzene,  phenylamine,  CqR^.^JI^' 

Was  first  obtained  in  1826  by  Unverdorben,  from  the  dry  distillation 
of  indigo,  and  termed  by  him  crystalline  "  ;  then  Eunge  found  it  in 
coal  tar  in  1834  and  called  it  ''cyanol."  In  1841  Fritsche  i^repared  it 
by  distilling  indigo  with  potash  and  gave  it  the  name  of  aniline,  while 
in  1842  Zinin  obtained  it  by  the  reduction  of  nitro-benzene  and  called 
it  "benzidam."  It  was  accurately  investigated  by  A,  W.  Hofmann 
in  1843. 


ANILINE. 


351 


Occurrence.    In  coal  tar  and  also  in  bone  oil. 

Preparation.  Since  1864  aniline  has  been  prepared  on  a 
manufacturing  scale  by  reducing  nitro -benzene  with  iron 
filings  and  a  regulated  quantity  of  hydrochloric  acid,  and 
distilling  with  steam.  It  is  a  colourless,  oily,  strongly  refract- 
ing liquid  of  weak  but  peculiar  odour,  which  quickly  turns 
yellow  or  brown  in  the  air  and  is  finally  converted  into  a 
resin.  M.  Pt.  -8°,  B.  Pt.  184°,  Sp.  Gr.  1-036.  It  dissolves 
in  31  parts  of  water,  has  no  action  upon  litmus,  and  is  a 
weaker  base  than  ammonia  in  the  cold,  but  displaces  the 
latter  at  higher  temperatures.  It  is  poisonous,  burns  with 
a  smoky  flame,  and  is  a  good  solvent  for  many  compounds 
which  are  otherwise  difficult  of  solution,  e.g,  indigo  and 
sulphur.    The  salts  have  an  acid  reaction. 

The  behaviour  of  aniline  has  been  investigated  with  the 
utmost  care.  Oxidation  in  alkaline  solution  leads  to  azo- 
benzene,  while  arsenic  acid  produces  chiefly  violaniline, 
C^gHj^Ng,  a  violet  colouring  matter  which  also  results  under 
the  oxidizing  influence  of  nitro-benzene.  A  solution  of  free 
aniline  is  temporarily  coloured  violet  by  one  of  bleaching 
powder,  this  reaction  being  an  extremely  delicate  one.  A  solu- 
tion in  concentrated  HgSO^  is  first  coloured  red  and  then  blue 
b}^  a  small  grain  of  bichromate  of  potash.  A  solution  of 
KgCrgO^  produces  in  an  acid  solution  of  aniline  sulphate  a 
dark  green  and  then  a  black  precipitate  of  aniline  black, 
which  finally  goes  into  quinone,  CgH^Og.  A  mixture  of  aniline 
and  toluidine  is  oxidizable  to  fuchsine,  mauveine,  etc.,  and 
a  mixture  of  aniline  and  ^-diamines  to  safranines  (p.  503). 

Chlorine  yields  trichlor-aniline  and  iodine  mon-iodo-aniline,  while 
chlorate  of  potash  and  hydrochloric  acid  produce  chloranil.  For  the 
action  of  NgOg,  see  diazo-compounds  ;  of  HNO3,  nitraniline ;  and  of 
H2SO4,  sulphanilic  acid.  When  aniline  is  heated  with  glycerine  and 
concentrated  sulphuric  acid  in  the  presence  of  nitro-benzene,  quinoline 
is  obtained  ;  when  it  is  boiled  with  sulphur,  thio-aniline,  (CgH4.NH2)2S  ; 
and  when  it  is  heated  with  urea,  diphenyl-urea,  CO(NHC6H5)2,  with 
elimination  of  NH3.  Many  reactions  analogous  to  the  last-named  are 
known. 

Salts.    Aniline  hydrochloride,  CgH5.NH2,  HCl:  large  colour- 


352 


XX.  AMIDO-COMPOUNDS. 


less  tables  which  become  greenish-grey  in  the  air  and  distil 
unchanged.  Aniline  sulphate,  (CgH^N)2H2S04  :  beautiful 
white  pjates,  difficultly  soluble  in  water.  The  double  salt 
with  platinic  chloride,  (CgH^N,  HC1)2,  PtCl^,  crystallizes  in 
moderately  soluble  yellow  plates. 

Substitution  Products  of  Aniline. 

Aniline  is  much  more  readily  substituted  by  halogens  than  benzene, 
an  aqueous  solution  of  chlorine  or  bromine  causing  substitution  of 
as  many  as  three  atoms  of  hydrogen,  while  iodine  produces  mono- 
iodaniline.  In  the  preparation  of  mono-chlor-  (or  brom-)  aniline,  the 
aniline  must  be  protected"  by  using  it  in  the  form  of  its  acetyl 
compound,  acetanilide.  When  this  is  suspended  in  water,  it  is  mostly 
transformed  by  chlorine  into  jo-chlor-acetanilide,  which  readily  yields 
p-chlor- aniline  on  saponification  ;  the  latter  forms  colourless  crystals, 
M.  Pt.  75°,  B.  Pt.  235°.  The  o-  and  m-compounds,  which  are  both 
liquid,  are  prepared  indirectly,  e.g.  by  the  reduction  of  o-  or  m-chloro- 
(or  bromo-)  benzene. 

The  basic  character  is  weakened  in  the  mono-chlor-  (and  brom-) 
anilines  by  the  entrance  of  the  halogen,  this  being  the  case  particularly 
in  the  o-compounds.  It  is  still  more  striking  in  a-triehlor-aniline, 
QH2Cl3(NH2)  (crystals,  volatile  without  decomposition),  which  no 
longer  combines  with  acids,  o-  and  p-chlor-anilines  are  only  capable 
of  taking  up  two  more  atoms  of  chlorine  with  the  formation  of  trichlor- 
aniline  :  NHgi  CI:  CI:  CI  =  1.2.4.6  ;  7?i-chlor-aniline,  on  the  other  hand, 
can  be  further  chlorinated  to  tetra-  and  penta-chlor-anUine. 

The  Brom-anilines  resemble  these  in  every  respect. 

Nitmnilines, 

Aniline  is  likewise  attacked  far  more  violently  than  benzene 
by  concentrated  nitric  acid,  and  therefore,  when  it  is  wished 
to  prepare  the  mono-nitro-compounds,  the  aniline  must  again 
be  ^*  protected,"  either  by  using  its  acetyl  compound  or 
by  nitrating  in  presence  of  excess  of  concentrated  sulphuric 
acid.  In  the  latter  case  all  three  nitranilines  result,  the 
m-compound  preponderating.  When  acetanilide  is  nitrated, 
2?-Nitracetanilide,  CgH4(N02)(NH.C2H30),  together  with  some 
of  the  o-compound,  result,  both  of  them  being  easily  saponified 
by  potash  or  hydrochloric  acid. 


NITRANILINES,  ETC. 


353 


The  0-  and  j9-nitranilines  are  also  formed  upon  heating  o-  and 
p-chloro-  or  bromo-nitro-benzenes,  or  the  ethers  of  the  correspondhig 
0-  and  29-nitro-phenols,  C6H4(N02)(O.C2H5),  or  these  nitro-phenols  them- 
selves with  ammonia  to  180°,  (cf.  B.  19,  1749).  o-Nitraniline  may  also 
be  prepared  by  nitrating  acetyl-sulphanilic  acid,  (B.  18,  294). 

The  nitranilines  are  further  obtained  by  the  partial  reduction 
of  the  corresponding  dinitro-benzenes,  e.g,  by  means  of  sul- 
phide of  ammonium. 

The  three  nitranilines  crystallize  in  yellow  needles  or 
prisms,  readily  soluble  in  alcohol  but  only  very  slightly  in 
water,  (cf.  table,  p.  341).  The  o-  and  m-compounds  are 
volatile  with  steam,  but  not  j?-nitraniline.  They  go  into 
phenylene-diamines  on  reduction. 

The  0-  and  ^-nitranilines  are  converted  into  nitro-phenols  when 
boiled  with  alkalies,  the  former  more  easily  than  the  latter,  thus  : 

C6H4(N02)(NH2)  +  H.OH       C6H4(N02)OH  +  NH3. 

Di-  and  tri-nitranUines,  C6H3(N02)2(NH2)  and  C6H2(N02)3(NH2),  are 
likewise  known  ;  the  latter,  which  is  termed  Picramide,  and  which 
crystallizes  in  yellow  needles,  M.  Pt.  186°,  comports  itself  as  the  amide 
of  picric  acid,  since  it  is  readily  transformed  into  the  latter  compound 
by  saponifying  agents,  (cf.  p.  318). 

^9 -Nitroso -aniline,  CgH4(NO)NH2,  is  formed  by  the  action  of  am- 
monium acetate  upon  ^-nitroso-phenol,  OH  being  exchanged  for  NHg. 
It  crystallizes  in  blue  needles,  and  is  very  similar  to  nitroso-dimethyl- 
aniline  in  behaviour,  (cf.  p.  322,  also  B.  20,  2471). 

For  Aniline-sulphonic  acids,  see  p.  375. 


Alkylated  Anilines. 

Methyl-aniline,  CgH5NH(CH3),  (Hofmann),  is  obtained  from 
the  methyl-aniline  of  commerce  (from  aniline  hydrochloride 
and  methyl  alcohol)  either  by  means  of  its  nitroso-compound 
or  as  given  at  p.  345,  (cf  B.  10,  327,  588).  It  is  lighter  than 
water,  and  has  an  odour  like  that  of  aniline  but  stronger  and 
more  aromatic. 

Its  sulphate  is  soluble  in  ether  and  non-cry stallizable.  A  solution 
of  bleaching  powder  colours  it  violet  and  then  brown.  For  its  ti  ans- 
formation  into  p-toluidiue,  see  p.  343. 

(50G)  i5 


354 


XX.  AMIDO-COMPOUNDS. 


Methyl-aniline-nitrosamine,  C6H5.N(NO)(CH3),  is  a  yellow  oil  of 
aromatic  odour  without  basic  properties,  which  can  be  distilled  with 
steam  but  not  alone.  It  shows  the  Liehermann  (nitroso)  reaction, 
giving  an  intensive  **  king's-blue  "  colouration  when  it  is  warmed  with 
phenol  and  sulphuric  acid,  and  the  mixture  then  diluted  with  water 
and  saturated  with  caustic  potash.  This  reaction  is  characteristic  of 
all  the  nitrosamines  and  of  many  other  nitroso-compounds.  Under  the 
influence  of  alcoholic  hydrochloric  acid  it  undergoes  molecular  trans- 
formation into  ;9-nitroso-monomethyl-aniline,  C6H4(NO) — NH.CH3, 
a  compound  precisely  similar  to  nitroso-dimethyl-anlline  and  crystalliz- 
ing in  green  plates  or  steel  blue  prisms. 

Di-methyl-aniline,  CgH5.N(CH3)2,  (Hofmann\  is  an  oil  of 
sharp  basic  odour,  solidifying  in  the  cold.  Its  salts  are  not 
crystallizable.  It  combines  with  methyl  iodide,  even  in  the  cold, 
to  the  compound  N(CgH5) (0113)31,  which  breaks  up  into  its 
components  upon  distillation.  The  corresponding  ammonium 
base  is  mentioned  on  p.  348.  Bleaching  powder  only  colours 
dimethyl-aniline  a  pale  yellow.  The  H-atom  in  it,  which  is 
in  the  j?-position  as  regards  the  N(CH3)2,  is  easily  exchange- 
able, e.g.  for  a  nitroso-group,  when  acted  on  by  NgOg. 
Dimethyl-aniline  consequently  yields  compounds  of  somewhat 
complex  composition  with  acid  chlorides,  aldehyde,  etc. ;  for 
example,  tetramethyl-diamido-benzophenone  or,  finally,  methyl 
violet  with  carbonyl  chloride,  COClg,  leuco-malachite  green 
with  benzoic  aldehyde,  etc.  Mild  oxidizing  agents,  such  as 
chloranil,  convert  it  into  methyl-violet. 

p-Nitroso-dimethyl-aniline,  C6H4(NO).N(CH3)2,  crystallizes  in  beauti- 
ful green  plates  or  tables  of  M.  Pt.  85° ;  its  HCl-salt  forms  yellow 
needles.  It  is  used  for  the  preparation  of  dyes  (methylene  blue, 
indophenol,  toluylene  red).  It  is  oxidized  by  KMn04  or  KgFeCyg  to 
2>Nitro-dimethyl-anmne,  C6H4(N02).N(CH3)2,  M.  Pt.  162°  (a  compound 
which  is  also  obtained  directly  together  with  the  m-compound  by  the 
nitration  of  dimethyl-aniline),  and  is  reduced  by  nascent  hydrogen  to 
amido-dimethyl-aniline,  C6H4(NH2).N(CH3)2,  which  belongs  to  the 
p-diamines  (p.  360).  Boiling  with  soda  converts  it  into  nitroso-phenol 
and  dimethylamine.    Since  nitroso-phenol  probably  has,  according  to 

p.  384,  the  formula  C6H4<^^^^^^  (quinone-oxime),  the  nearly  related 

nitroso-dimethyl-aniline  and  its  hydrochloride  may  possibly  have  the 
following  formula?,  (cf.  B.  20,  532) : 


DI-  AND  TRIPHENYLAMINES. 


355 


The  free  base. 


>0. 


The  hydrochloride. 


Di-  and  Tri-phenylamines, 


Diphenylamine,  (CgH5)2NH,  {Hofmann),  crystallizes  in  white 
plates  of  flowery  odour  and  burning  taste  which  are  almost 
insoluble  in  water,  but  readily  soluble  in  alcohol,  ether  and 
ligroin.  The  hydrochloride,  C^g^ii^j  HCl,  is  a  white 
crystalline  meal  which  turns  blue  in  the  air.  A  solution 
of  diphenylamine  in  concentrated  HgSO^  is  coloured  an  in- 
tensive blue  by  traces  of  nitric  acid,  this  reaction  being  a  very 
delicate  test  for  the  latter.  When  diphenylamine  is  heated 
with  formic  acid  and  zinc  chloride,  it  yields  acridine.  It  is 
used  for  the  preparation  of  diphenylamine  blue. 

Diphenyl-nitrosamine,  {C6Hg)2N.NO,  is  obtained  by  the  use  of  ethyl 
nitrite  and  crystallizes  in  bright  glancing  yellowish  tables.  o-Dinitro- 
diphenylamine,  (C6H4.N02)2NH,  forms  red  needles,  and  the  analogous 
p-compound  yellow  prisms.  Hexa -nitre -diphenylamine  crystallizes  in 
yellow  prisms  and  has  the  properties  of  a  weak  acid,  this  being  due  to 
the  acidfying  influence  of  the  nitro-groups  upon  the  imido-hydrogen ; 
its  ammonium  salt  is  the  yellow  dye  Aurantia.  For  the  Amide-  and 
Oxy-cempeunds  of  diphenylamine,  which  are  tabulated  on  p.  341,  and 
the  colouring  matters  derivable  from  them,  see  also  safranine  and 
indophenol  (p.  356). 

Methyl-diphenylamine,  (CeHgjaN.CHo,  is  a  liquid  which  results  on 
methylating  diphenylamine ;  it  also  is  employed  on  a  manufacturing 
scale. 

TMe-diphenylamine,  C12H9NS,    =   NH<p6H^4^g^  ig  obtained  by 

heating  diphenylamine  with  sulphur.  Yellowish  plates  ;  M.  Pt.  180°. 
May  be  distilled  unchanged. 

Triphenylamine,  N(  €6115)3,  forms  large  tables. 


Colour  Derivatives  of  Di-phenylamine. 

{a)  The  Methylene  Blue  group. 
Thio-diphenylamine,    which   resembles   anthracene,   acridine  and 


356 


XX.  AMIDO-COMPOUNDS. 


phenazine  in  constitution,  is  a  chromogene"  (see  p.  24),  since  it  is 
converted  into  leuco-compounds  of  colouring  matters  by  the  entrance  of 
NH2,  N(CH3)2,  OH,  etc.  (cf.  rosaniline).    Thus  Diamido-thio-diphenyl- 

CeH3— 

amine  or  Leuco-thionine,  HN<"        >S     ,  is  the  leuco-compound  of 
CgHs— NH2 

Thionine,  N'<^  ,  whose  HCl  salt  is  Lauth's  Violet ;  and  the 

I  ^C«H,— NH 


hydrochloride  of  Methylene  Blue  {Caro,  1876),  a  very  valuable  blue  dye, 

C6H3— N(CH3)2 

especially  for  cotton,  has  the  constitution  N<^  , 

I  ^CeHa— N(0H3)2C1 


J 


{Bernthsen,  A.  230,  1 ;  cf.  also  pp.  350  and  360.) 


(b)  Indamines  and  Indophenols. 

As  Indamines  are  designated,  according  to  Nietzhi,  those  green  or  blue 
colouring  matters  which  are  produced  by  the  action  of  nitroso-dimethyl- 
aniline  upon  amines,  e.g.  dimethyl-aniline,  or  by  the  conjoint  oxidation 
of  p-diamines  and  monamines  in  the  cold. 

The  simplest  representative  of  this  class  is  the  indamine  '*Plienylene 
Blue,"  C12H11N3,  =  N<^6H4-NH2^  which  results  from  the  oxidation  of 

a  mixture  of  aniline  and  /?-phenylene-diamine,  and  is  converted  by 
reduction  into  ^j-diamido-diphenylamine,  NH(CgH4.NH2)2  (p.  341). 

Dimethyl-phenylene  Green,"  CigHi9N3,  is  obtained  in  an  analogous 
manner  from  ^^-amido-dimetliyl-aniline  and  dimethyl-aniline,  and  yields 
tetramethyl-diamido-diphenylamine,  NH[C6H4.N(CH3)2]2  (p.  341),  on 
reduction.  The  indamines  are  unstable  compounds  but  are  of  import- 
ance as  being  intermediate  products  in  the  manufacture  of  safranine. 

Oxygenated  compounds,  WiW^s  ''Indophenols,"  are  likewise  derived 
here  by  the  exchange  of  NH2  or  N(CH3)2  for  OH,  which  is  achieved  by 
warming  with  alkali ;  e.g.  Phenol  Blue  (indo-aniline),  N<;^6H4.N(CH3)2^ 

is  produced  by  the  oxidation  of  amido-dimethyl-aniline  with  phenol. 
Its  analogue,  a-Napthol  Blue,  N<^&^''^^^3^2^  prepared  by  means  of 


napthol  (p.  466),  is  a  colouring  matter  which  finds  technical  application. 
Such  compounds  exchange  N(CH3)2  for  OH  when  boiled  with  a  solution 
of  NaOH  ;  thus,  from  phenol  blue  there  results  Indophenol  ("  quinone- 


ANILIDES. 


357 


phenol-imide  "),  N<^^y4-^^^  a  dye  of  phenolic  nature  (p.  376),  which 


dissolves  in  alcohol  to  a  red,  and  in  alkali  or  ammonia  to  a  blue  solution. 
It  may  also  be  obtained  by  the  action  of  phenol  upon  quinone  chlor- 
imide  (see  quinones)  : 

yO  /O  /C6H4.OH 

C,h/  I       +  CeHgOH  =  CeH  /  |  =  N<(  +  H( 

\n.C1  \N-C6H4.OH,        I  NC6H4.O 

Quinone  I  I 

chlor-imide.  Indophenol. 

and  also  by  the  oxidation  of  p-amido-phenol  with  phenol.  Its  leuco- 
compound  is  /^-Dioxy-diphenylamine,  NH(C6H4.0H)2,  a  substance  which 
unites  in  itself  the  properties  of  diphenylamine  and  a  diatomic  phenol. 
(Seep.  376;  of.  B.  16,  2843;  18,  2912.) 


Acid  Derivatives  of  Aniline,  Anilides. 

Acetanilide,  CgHj^.NH.(C2H30),  is  most  conveniently  pre- 
pared by  boiling  aniline  with  glacial  acetic  acid  for  several 
days.  It  crystallizes  in  beautiful  white  prisms  which  are 
readily  soluble  in  hot  water,  alcohol,  ether  and  benzene ; 
M.  Pt.  115%  B.  Pt.  295°.  It  is  easily  saponifiable  (cf.  p.  345). 
Its  imido-hydrogen  is  replaceable  by  sodium  with  the  formation 
of  the  crystalline  Sodium-acetanilide,  CgH5.N.Na(C2H30), 
which  is  again  decomposed  by  water  (see  p.  181).  Acetanilide 
is  used,  under  the  name  of  **antifebrine,"  as  a  medicine  in 
cases  of  fever. 

TMo-acetanilide,  CH3 — CS.NHCgHg,  results  upon  heating  acetanilide 
with  P2S5  (analogously  to  aceto-thiamide,  p.  184),  and  from  it  Imido- 
thio-compounds,  Amidines,  etc.  can  be  prepared  (cf.  p.  185).  Acetanilide 
yields  the  dye  Flavaniline  when  heated  with  zinc  chloride. 


In  nearly  all  those  compounds  of  the  fatty  series  which  are 
ammonia  derivatives  of  alcohols,  acids  or  alcohol-acids,  and 
which  still  contain  unreplaced  ammoniacal  hydrogen,  the 
latter  can  be  substituted  either  wholly  or  partially  by  phenyl, 
for  the  most  part  indirectly.    The  number  of  these  phenylated 


358 


XX.  AMIDO-COMPOUNDS. 


(tolylated,  xylylated,  etc.)  compounds  is  thus  extremely  large. 
Among  them  may  be  mentioned  : 
 NH  C  H 

Phenyl-glycocoU,  *  ^  ^,  from  chloracetic  acid  and  aniline  ; 

CO  'OH 

Phenyl-imido-butyric  acid,  CH3— ClNCeHg) — CH^— CO2H,  from  aniline 
and  aceto-acetic  ether ;  Carbanilide  or  diphenyl-urea,  CO(NHCgH5)2, 
from  aniline  and  carbon  oxy chloride,  (cf.  p.  272) ;  Phenyl  cyanate, 
COiN.CgHg,  a  sharp-smelling  liquid  exactly  analogous  to  the  cyanic 
ethers,  and  whose  vapour  gives  rise  to  tears,  from  COCI2  and  fused 
aniline  hydrochloride  ;  Phenyl  isothio cyanate,  CeHgNiCS,  (B.  Pt.  220"), 
a  liquid  possessing  all  the  characteristics  of  the  mustard  oils ;  Diphenyl- 
thio-urea,  CS(NHC6H5).2,  from  aniline  and  carbon  bisulphide,  (glancing 
plates,  M.  Pt.  154°,  decomposed  into  phenyl  isothiocyanate  and  tri- 
phenyl-guanidine  by  boiling  with  concentrated  HCl) ;  Mono-,  Tri-,  and 
Tetra-phenyl-thio-ureas ;  Phenylated  guanidines,  etc.,  (cf.  table,  p.  341). 


Eomologues  of  Aniline. 

1.  The  three  Toluidines,  C6H4(CH3)(NH2),  result  from  the 
reduction  of  the  three  nitro-toluenes,  ^-toluidine  (Musjpratt  and 
Hofmann,  1845)  being  solid,  and  o-toluidine  liquid;  they  are 
also  present  in  coal  tar. 

The  crude  nitro-toluene  of  commerce  yields  a  mixture  of  0-  and  p- 
with  a  little  m-toluidine  upon  reduction  ;  the  two  first  may  be  separated 
from  one  another,  e.g.  by  taking  advantage  of  the  relatively  sparing 
solubility  of  p-toluidine  oxalate,  (cf.  B.  16,  908). 

m-Toluldine,  which  is  liquid,  may  be  prepared  from  m-nitro- 
toluene  or  m-nitro-benzaldehyde,  (cf  B.  15,  2009). 

The  boiling  points  of  the  three  isomeric  toluidines  are  almost 
identical  (see  table,  p.  341),  but  the  melting  points  of  their  acetyl 
compounds  differ  widely,  the  o-compound  melting  at  107°,  the  p-  at 
147°,  and  the  m-  at  65° ;  these  are  therefore  of  value  for  the  character- 
ization of  the  toluidines.  o-Toluidine  is  coloured  violet  by  a  solution 
of  chloride  of  lime,  and  blue  by  sulphuric  and  nitrous  acids  and  also  by 
ferric  chloride,  but  not  ^-toluidine.  For  their  conversion  into  fuchsine 
by  oxidation,  see  p.  451.  If,  during  oxidation,  the  amido-group  be 
protected  by  the  introduction  of  acetyl,  the  methyl  can  be  oxidized 
to  carboxyl  and  in  this  way  an  (acetyl  derivative  of)  amido-benzoic  acid 
obtained,  while  the  amido-compounds  are  transformed  into  azo-com- 
pounds  by  KMn04. 


BENZYLAMINE,  ETC.  ;  DI-  AND  TRIAMINES.  35d 


Compounds  such  as  Methyl-  and  dimethyl-p-toluidines,  acet-toluide, 
C(.H4(CH3).NH(C2H30),  di-tolylamine,  (C(.H4.CH3),NH,  phenyl-tolyl- 
amine,  NH[C6H5](C6H4.CH3),  nitre -toluidines,  C6H3(CH3)(NO,)(NH2), 
etc.,  have  been  prepared  in  large  numbers,  and  are  in  every  respect 
similar  to  the  corresponding  phenyl  compounds. 

2.  Isomeric  with  the  toluidines  is  : 

Benzy lamina,  CgH^ — CH2.NH2,  the  alcoholic  amine  of 
benzyl  alcohol,  a  colourless  basic  liquid  which  distils  un- 
changed. It  is  best  prepared,  at  first  as  the  acetyl  com- 
pound, CgHg — CH2.NII(C2H30),  by  heating  benzyl  chloride, 
C^jHg — CH2CI,  with  acetamide,  NH2(C2H30).  Its  behaviour 
is  entirely  analogous  to  that  of  methylamine,  as  the  phenyl 
derivative  of  which  it  is  to  be  regarded,  (cf.  p.  346). 

3.  Xylidlnes,  £[3(0113)2.  NH2.  According  to  theory,  these  may 
exist  in  six  modifications,  all  of  which  are  known.  Amido-o -xylene 
(CHgiCHgiNHa  =  1:2:4)  is  solid,  melting  at  49°,  while  the  other  five 
are  liquid.  The  boiling  points  lie  between  212°  and  226°.  The  xylidine 
of  commerce  contains  five  of  these  compounds,  but  principally  m-xylidine 
(CH3:CH3:NH2  =  1:3:4),  B.  Pt.  212°,  and  p-xylidine  (1:4:2) ;  it  is  used 
for  the  manufacture  of  azo-dyes. 

4.  Amido-trimethyl-benzenes,  C6H2(CH3)3NH2.  The  hydrochloride 
of  amido-trimethyl-benzene  is  formed  when  HCl-xylidine  is  heated  with 
methyl  alcohol  to  about  300°.  In  this  way  there  have  been  prepared  \|/- 
(Pseudo-)cumidine  or  amido-pseudo-cu7nene{  CHg  :CH3  :CH3:NH2  =  1 :2 :4 :5), 
M.  Pt.  63°,  B.  Pt.  235°,  and  Mesidine  or  ajnido -mesitylene  {l:S:5:2),  a> 
liquid,  B.  Pt.  230°.  i/'-Cumidine  is  also  used  for  manufacturing  azo- 
dyes. 

Isomeric  with  the  above  bases  are  amide  -  ethyl  -  benzene 
C6H4.(NH2)(C2H5),  and  amido-propyl  benzene,  C6H4(NH2)(C3H7),  of 
which  the  /^-modifications,  for  instance,  are  obtained  by  heating  aniline 
with  the  alcohol  in  question  and  chloride  of  zinc. 

5.  Amido-isobutyl-benzene,  C6H4(NH2)(C4Hc)),  has  likewise  been 
prepared. 

Tetramethyl-amido -benzenes  {amido-durene,  prehnidine), 
C6H(NH2)(CH3)4,  m-isocymidine,  C6H3(NH2)(CH3)(C3H7),  and  penta- 
methyl-amido-benzene,  C6(NH2)(CH3)5,  are  also  known. 


Diamines,  Triamines,  etc. 

Of  the  Phenylene- diamines,  C6H4(NH2)2,  the  meta-compound  (Zininy 
1844)  is  the  most  easily  prepared,  by  reducing  m-dinitro-benzene.  It 


360     XXI.  DIAZO-  AND  AZO-COMPOUNDS  ;  HYDRAZINES. 


crystallizes  in  tables.  Nitrous  acid  converts  it  into  Bismarck  brown, 
the  presence  of  the  merest  trace  of  this  acid  being  shown  by  the  yellow 
colouration  it  gives  with  the  diamine,  (cf.  B.  14,  1015).  Para- 
phenylene- diamine  {Hofmann,  1863),  crystallizes  in  plates  and  its 
HCl-salt  in  white  tables  ;  an  acid  solution  of  it  yields  the  violet  dye 
thionine  (p.  356)  with  H^S  and  FegClg.  Its  unsymmetrical  dimethyl- 
derivative,  p-amido- dimethyl-aniline,  C6H4(NH2)[N(CH3)2],  which  may 
be  prepared  as  given  at  p.  349,  but  most  easily  by  the  reduction  of  the 
azo-dye  helianthin  (p.  371  ;  B.  16,  2235),  gives  methylene  blue  with 
Fe^Cle  and  H2S,  this  being  the  most  delicate  test  for  sulphuretted 
hydrogen  known,  and  it  is  coloured  a  magnificent  purple  by  FegCIg 
in  dilute  neutral  solution.  Ortho-phenylene- diamine  (Griess,  1861), 
is  transformed  into  hydro-phenazine  (p.  502)  when  heated  with  pyro- 
catechin. 

o-p-Toluylene- diamine,  C6H3(CH3)(NH2)2  (1:2:4),  is,  as  a  m-diamine, 
easily  obtained  by  reduction  of  the  common  dinitro-toluene  (p.  338). 
It  is  used  for  the  preparation  of  toluylene  red,  etc.  m-^-Toluylene- 
diamine,  C6H3(CH3)(NH2)2  (1:3:4),  is  the  o-diamine  which  is  most  easily 
prepared,  viz.,  by  nitrating  acet-^-toluide,  saponifying  and  reducing. 

The  Xylylene-diamines,  CeH2(CIl3)2(NH2)2,  are  homologous  with  the 
above. 


XXI.   DIAZO-  AND  AZO-OOMPOUNDS ; 
HYDRAZINES. 

A.  Diazo-Oompounds. 

The  primary  amido-compounds  of  the  benzene  series  differ 
characteristically  from  those  of  the  fatty  series  in  their 
behaviour  towards  nitrous  acid.  The  latter  are  converted 
into  alcohols  by  NgOg  without  the  formation  of  intermediate 
products,  (cf.  p.  114): 

C2H5.NH2  +  NO.OH  =  C2H5.OH  +  N2  +  H2O. 

The  aromatic  amines  can  indeed  undergo  an  analogous 
transformation,  but  there  result  in  their  case  well-characterized 
intermediate  products,  the  so-called  diazo-compounds,  which 
are  of  especial  interest  both  scientifically  and  technically 
(cf.  p.  379).    They  were  discovered  by  P.  Griess  in  1860 


DIAZO-COMPOUNDS  ;  FORMATION. 


361 


and  were  carefully  investigated  by  him,  (A.  121,  257;  137, 
39) ;  their  constitution  was  elucidated  by  KekulL 

Formation,  When  nitrogen  trioxide  is  led  into  a  cream 
of  aniline  nitrate  and  dilute  nitric  acid,  the  aniline  salt 
dissolves  and  a  liquid  is  obtained  from  which  alcohol  and 
ether  precipitate  beautiful  long  white  needles  of  diazo-benzene 
nitrate,  (CgH5N2).N03.  These  are  tolerably  stable  in  dry  air 
but  quickly  decompose  in  moist,  and  they  are  distinguished 
by  the  violence  with  which  they  explode  when  heated  or 
struck.  The  base  itself,  diazo-benzene  (p.  364),  appears  to 
have  the  formula  (CgH^ — N2)0H,  just  as  the  base  KOH 
corresponds  to  the  salt  KNO3. 

In  a  similar  manner  other  salts  of  diazo-benzene,  e,g.  the 
chloride,  CgH^Ng.Cl,  and  the  sulphate,  (CgH5N2).S04H,  are 
obtained  from  aniline  hydrochloride  and  sulphate  in  the 
presence  of  free  acid.  Double  salts  with  PtCl^,  AuClg,  etc.,  are 
also  known.  The  homologues  of  aniline  and  the  diamines  show 
a  similar  behaviour,  e.g.  ^-toluidine  yields  salts  of  diazo-toluene, 


Most  of  the  diazo-compounds  are  prepared  only  in  aqueous 
solution,  and  not  in  the  solid  form,  on  account  of  their 
instabihty  and  tendency  to  explode.  One  mol.  aniline,  for 
instance,  is  dissolved  in  two  or  more  mols.  hydrochloric  acid,  and  the 
calculated  quantity  of  a  solution  of  sodium  nitrite  is  allowed  to  flow 
into  it,  the  whole  being  cooled  by  ice.  The  liquid  must  remain  clear 
and  no  nitrogen  to  speak  of  must  be  evolved.  Any  excess  of  nitrous 
acid  can  be  got  rid  of  by  blowing  air  through  the  solution.  Occasionally 
the  amido-compound  dissolved  in  concentrated  sulphuric  acid  is  treated 
with  NgOg. 

The  formation  of  the  diazo-compounds  is  shown  by  the 
following  equation : 


Diazo-benzene  nitrate. 

The  conversion  of  amido-  into  diazo-compounds  is  termed 
diazotizing." 

The  constitution  of  the  diazo-compounds,  e.g.  CgH^-N^N-Cl 
or  CgH^N=N — SO4H,  follows  especially  from  these  two  re- 


e.g.  CeH4(CH3)N2.CL 


N;02H  I 


3 


=  CeH,.N=N.N03  +  2H2O. 


362     XXI.  DIAZO-  AND  AZO-COMPOUNDS ;  HYDRAZINES. 


actions  :  1.  from  their  transformation  into  hydrazines  upon 
reduction;  2.  from  the  formati  n  of  azo-dyes  by  the  action  of 
diazo-compounds  upon  many  amines  and  phenols. 

Many  of  the  properties  shown  by  the  diazo-compounds  admit  of 
an  easier  explanation  if  one  makes  the  assumption  that  they  are  also 
capable  of  reacting  as  if  they  were  constituted  according  to  the  other 
hypothetical  formula,  CgHg — NH — NO  (  =  free  diazo-benzene),  or 

CgHg— NH— N<^p  (diazo-benzene  chloride)  (Caro,  Ost.;  cf.pp.  265-6). 

Behaviour.  1.  Towards  water.  An  aqueous  solution  of  a 
diazo-salt,  especially  one  containing  sulphuric  acid,  gives  off 
all  its  nitrogen  in  the  form  of  gas  upon  warming,  and  there 
results  a  phenol,  thus  : 

^^iN=N|gl  ^  (.^jj^  Qjj  ^^^^ 

This  reaction,  which  is  of  very  universal  application,  there- 
fore allows  of  the  exchange  of  amidogen  for  hydroxyl. 

2.  Towards  alcohol.  When  diazo-compounds,  either  in  the 
solid  state  or  dissolved  in  concentrated  sulphuric  acid,  are 
heated  to  boiling  with  absolute  alcohol,  the  diazo-group  is 
generally  replaced  by  hydrogen.  In  this  reaction  the  alcohol 
gives  up  two  atoms  of  hydrogen  and  goes  into  aldehyde : 


+  H 


=  C^He  +       +  HCl. 


By  this  means  we  are  enabled  completely  to  eliminate  a 
diazo-group  and  therefore  an  amido-  one  from  a  benzene 
derivative. 

Instead  of  this  reaction  there  occurs  in  many  cases  an  exchange  of 
the  diazo-group  for  the  alcohol  radicle,  O.CgHg,  with  the  formation  of 
ethyl  ethers  of  phenol ;  thus  chlorinated  cresoi  ethyl  ether  results,  in 
place  of  chloro-toluene,  from  chlorinated  toluidines,  (B.  17,  2703;  21, 
978). 

2a.  Under  certain  conditions  stannous  chloride  acts  in  an  analogous 
manner,  while  under  others  it  gives  rise  to  hydrazines  (p.  372). 

26.  In  like  manner  NHg  may  be  replaced  by  H,  by  first  converting 
an  amido-compound  into  a  hydrazine  and  then  decomposing  the  latter 
with  CUSO4,  (Baeyer). 

3.  When  a  diazo-compound  is  warmed  with  a  concen- 


DIAZO-COMPOUNDS  ;  BEHAVIOUR. 


363 


trated  solution  of  cuprous  chloride  in  hydrochloric  acid,  the 
diazo-group  is  replaced  by  chlorine  {Sandmeyer,  B.  17,  1673); 
the  same  reaction  takes  place  on  distilling  the  platinum  double  salt  of 
the  diazo-compound  with  soda,  and  sometimes  on  simply  treating  the 
diazo- compound  itself  with  fuming  hydrochloric  acid  : 

CeH^.N^N.Cl  =  CgH.Cl  +  Ng. 

4.  Warming  with  cuprous  bromide  yields  in  the  same  way 
a  bromine  compound  (Sandmeyer,  B.  18,  1482),  and  treatment 
with  hydriodic  acid  or  potassium  iodide  an  iodine  one,  while 
cuprous  cyanide  effects  an  exchange  of  the  amido-group  for 
cyanogen,  (B.  17,  2650) : 

2C,H5.N2.CI  +  Cu2Br2  =  2C6H5Br  +  Cu^Cl^  +  'N^; 
GqR,.^^.G\  +  KI  =  CgH^I  +  KCI  +      ;  etc. 

The  NHg-group  may  further  be  exchanged  for  Br  by  boiling  the 
diazo-perbromides  (see  diazo-benzene  perbromide)  with  absolute 
alcohol. 

Phenyl  sulphide  results  from  diazo-benzene  chloride  and  sulphuretted 
hydrogen,  (cf.  B.  15,  1683). 

The  reactions  1  to  4,  which  are  classed  together  under  the  name  of 
the  Griess  reaction,  are  invaluable  for  effecting  the  exchange  of  nitro- 
or  amido-groups  for  OH,  H,  CI,  Br,  I  and  CN,  and  are  constantly  made 
use  of  in  the  laboratory. 

The  diazo-group  is  also  exchangeable  for  the  nitro-  one, 
(Sandmeyer ;  cf.  also  p.  337). 

5.  When  a  diazo-compound  acts  upon  a  primary  or  secondary 
amine,  or  when  NgOg  acts  upon  such  an  amine  in  the  absence  of 
acid,  diazo-amido-compounds  result,  and  these  readily  change 
into  amido-azo-compounds.  The  latter  are  formed  directly  by 
the  action  of  the  diazo-compounds  upon  tertiary  amines  : 

CgHg.N^N.Cl  +  NHa.CgHg  =  HCl  +  CeHgJ^^N— NH.CgHg ; 

^  Y  ^ 

Diazo-amido-benzene. 

CeH5.N=N.Cl  +  CaH5.N(CH3),  =  HCl  +  CaH,-N=N-CsH4.  N(Cn,),. 

Dimethyl-amido-azobenzene. 

Analogous  reactions  also  take  place  with  the  Tw-diamines  and  with 
phenols,  oxy-azo-compounds  being  formed  in  the  latter  case,  (see  p.  368). 
The  production  of  the  orange-red  dye  by  the  action  of  diazo-compounds 
upon  m-phenylene-diamine  or  /3-naphthol  is  a  very  delicate  test  for  the 


364     XXI.  DIAZO-  AND  AZO-COMPOUNDS  ;  HYDRAZINES. 

presence  of  the  former.  Diazo-amido-compounds  only  show  this  reaction 
in  acetic  acid  solution. 


The  salts  of  the  diazo-compounds  are  colourless  and  frequently 
crystallize  well ;  they  often  decompose  with  violent  explosion  in  the 
air  or  upon  being  kept.  Most  of  them  are  easily  soluble  in  water, 
slightly  soluble  in  alcohol,  and  insoluble  in  ether. 

Diazo-benzene  nitrate,  CgHg — N=N.(N03)  (p.  361).    Long  needles. 

Diazo-benzene  sulphate,  C6H5.N=N.(S04H),  is  a  syrupy  mass  which 
solidifies  to  prisms  ;  it  explodes  at  160°. 

Diazo-benzene  perbromide,  06H5N=N.Br.Br2,  is  a  dark  brown  oil, 
solidifying  to  yellow  crystalline  plates,  which  results  upon  the  addition 
of  HBr  or  KBr  and  bromine  water  to  diazo-salts.  Two  of  its  atoms  of 
bromine  are  only  loosely  linked.  Ammonia  converts  it  into  diazo- 
benzene-imide,  thus  : 


When  concentrated  potash  solution  acts  upon  diazo-benzene  nitrate, 
Diazo  benzene-potassium  oxide,  CgH5N=N(0K),is  formed.  It  crystallizes 
in  white  glancing  mother-of-pearl  plates,  readily  soluble  in  water  and 
alcohol  and  easily  decomposable,  and  from  its  aqueous  solution  metallic 
salts  precipitate  other  metallic  compounds,  e.g.  the  very  explosive 
Diazo-benzene-silver  oxide,  C6H5N=N— O.  Ag.  The  free  Diazo-benzene, 
C(jH5.N=N.0H,  is  precipitated  from  the  potassium  salt  by  acetic  acid 
as  a  heavy  oil  which  rapidly  decomposes  of  itself. 


The  diazo-amido-compounds  are  pale  yellow  crystalline 
substances  which  are  stable  in  the  air  and  do  not  combine 
with  acids. 

Formation,    See  preceding  page. 

Behaviour.  1.  The  diazo-amido-compounds  behave  in  pretty 
much  the  same  way  as  the  diazo-compounds,  since  they  are 
usually  broken  up  in  the  first  instance  into  their  components, 


C6H5.N=N.Br  +  Brg  =  fiHs.NBr— NBr, 


Diazo-benzene  perbromide. 
CeHg.NBr— NBra  +  NHg  =  C6H5.N<?  +  3HBr. 


Diazo-benzene-imide. 


B.  Diazo-amido-compounds. 


DIAZO-AMIDO-COMPOUNDS. 


365 


diazo-benzene  (salt)  and  amine,  the  former  then  entering  into 
reaction.  Thus  diazo-amido-benzene,  for  example,  yields 
phenol  and  aniline  when  boiled  with  water  or  hydrochloric 
acid,  while  with  hydrobromic  acid  it  gives  bromo-benzene  and 
aniline. 

These  reactions  are  easy  to  recognise  from  the  accompanying  evolu- 
tion of  nitrogen. 

2.  By  the  renewed  action  of  nitrous  acid  in  acid  solution,  they  are 
completely  transformed  into  diazo- compounds,  e.g.  : 

C6H5.N2.NH.C6H5  +  NO2H  +  2HC1  -  2CeH5.N2.Cl  +  2H2O. 

3.  Most  of  them  readily  undergo  molecular  transformation 
into  the  isomeric  amido-azo-compounds,  {KekuU). 

This  molecular  rearrangement  takes  place  particularly  easily  in  pre- 
sence of  an  amine  hydrochloride,  which  is  explained  by  the  action  of  the 
latter  upon  the  diazo-amido-compound,  thus  : 

CeH,.N,.NH.C(,H5  +  CeH^-NH^  =  CeH^.N^.CeH^.NH^  +  CeH^.NH,. 

In  the  above  reaction  the  aniline  (i.e.  the  amine)  is  continually  being 
regenerated,  so  that  a  small  quantity  of  it  suffices  for  the  transforma- 
tion. The  nitrogen  of  the  amine  here  takes  up  the  para-position  with 
regard  to  the  azo -group  ( — N=N — ). 

This  molecular  rearrangement  is  easy  to  effect  in  the  case  of  the 
diazo-amido-compounds  of  aniline  and  also  in  those  of  o-  and  m-toluidine, 
but  more  difficult  in  the  case  of  the  79-compound  ;  in  p-toluidine  the 
para-position  is  already  taken  up  by  CH3,  so  that  another  position  (the 
ortho-)  must  be  occupied  here.    (Cf.  p.  371.) 

4.  The  imido-hydrogen  of  the  diazo-amido-compounds  is  replaceable 
by  Ag,  etc. 

Constitution.  By  the  action  of  diazo-benzene  chloride  upon  ^-tolui- 
dine  there  results  "diazo-benzene-^^-toluide,"  which  would  thus  appear 
to  possess  the  formula  : 

CgHg— N-N— NH— C7H7  (I.). 

But  the  same  compound  is  also  obtained  from  a  mixture  of  diazo - 
^-toluene  chloride  and  aniline,  a  reaction  which  would  indicate  its 
constitution  to  be  : 

CgHg— N  H— N = N— C7H7      (II. ). 

It  is  all  the  more  difficult  to  decide  which  of  these  two  formulae  is 
the  right  one,  from  the  fact  that  most  of  those  "mixed  diazo-amido- 
compounds  "  react  as  if  they  had  both  of  the  above  constitutions.  Thus, 
when  the  compound  just  mentioned  is  boiled  Avith  dilute  sulphuric  acid, 


366     XXI.  DIAZO-  AND  AZO-COMPOUNDS  ;  HYDRAZINES. 


it  yields  not  only  phenol  and  p-toluidine  (according  to  I.),  but  also 
aniline  and  p-cresol  (according  to  II.).  Cf.  e.g.  B.  19,  3239;  20,  3004; 
21,  548,  1016. 


Diazo-amido-benzene,  CgH^ — N=N— NHCgH^  (Griess). 

Preparation.  By  adding  NaNOg  (1  mol.)  to  the  solution  of 
aniline  (2  mols.)  in  HCl  (3  mols.),  and  saturating  with  sodium 
acetate,  (B.  17,  641). 

Properties.  Bright  yellow  glancing  plates  or  prisms,  insoluble 
in  water  but  readily  soluble  in  hot  alcohol,  ether  and  benzene. 
M.  Pt.  98°.    Far  more  stable  than  the  diazo-compounds. 

0.  Azo-compounds. 

While  the  reduction  of  nitro-compounds  in  acid  solution 
leads  to  the  aromatic  amines,  the  use  of  alkaline  reducing 
agents  such  as  sodium  amalgam,  zinc  dust  and  caustic  soda, 
and  also  potash  and  alcohol,  gives  rise  for  the  most  part  to 
intermediate  products,  the  azoxy-,  azo-  and  hydrazo-com- 
pounds  : 

CgHg — NO2,  Nitro-benzene. 
I  >0  II  I 

Azoxy -benzene.  Azo-benzene.  Hydrazo-benzene. 

CgHg— NH2,  Aniline. 

Of  these  the  azo-compounds  are  the  most  important. 

1.  Azoxy-compounds. 

The  azoxy-compounds  are  mostly  yellow  or  red  crystalline  substances 
which  result  from  the  action  of  alcoholic  potash,  and  especially  of 
potassium  methylate  (B.  15,  865),  upon  the  nitro-compounds.  Many  of 
them  may  also  be  obtained  by  the  oxidation  of  azo-compounds.  They 
are  of  neutral  reaction  and  are  very  readily  changed  into  azo-com- 
pounds, etc.  upon  reduction. 


HYDRAZO-  AND  AZO-COMPOUNDS. 


367 


Azoxy-benzene,  (06115)2X20  (Zinin),  forms  pale  yellow  needles  of 
M.  Pt.  86°,  insoluble  in  water  but  easily  soluble  in  alcohol  and  ether. 
Concentrated  sulphuric  acid  transforms  it  into  the  isomeric  ^9- oxy-azo- 
benzene,  C6H5N=N— C6H4OH. 

2.  Hydrazo-compounds. 

The  hydrazo-compounds  are  colourless,  crystalline  and  of 
neutral  reaction,  and — like  the  azo-compounds — they  cannot 
be  volatilized  without  decomposition ;  for  instance,  hydrazo- 
benzene  decomposes  into  azo-benzene  and  aniline  when  heated. 
They  are  obtained  by  the  reduction  of  azo-compounds  by 
sulphide  of  ammonium  or  zinc  dust.  Oxidizing  agents  such  as 
ferric  chloride  readily  transform  them  into  azo-compounds, 
into  which  they  also  change  slowly  in  the  air  alone.  The 
stronger  reducing  agents,  e.g.  sodium  amalgam,  convert  them 
into  amido-compounds. 

Strong  acids  cause  them  to  change  into  the  isomeric  deriva- 
tives of  diphenyl  (p.  438) ;  thus  from  hydrazo-benzene  and 
hydrochloric  acid  there  results  benzidine  chloride  (p.  439) : 

CeHg— NH— NH— CgH,  =  NH^-CeH^-CeH  — NH^ 

Benzidine. 

This  molecular  rearrangement  does  not  take  place,  or  at  least  only 
with  difficulty,  if  the  hydrogen  which  occupies  the  para-position  to  the 
imido-group  is  replaced  by  other  groups. 


Hydrazo-benzene,  CgHg— NH— NH— CgHg  (Hofmann),iorm^  colour- 
less plates  of  camphor-like  odour,  which  are  only  slightly  soluble  in 
water,  but  readily  soluble  in  alcohol  and  ether;  M.  Pt.  131°.  The 
imido-hydrogen  atoms  are  replaceable  by  acetyl-  or  nitroso-groups. 

3.  Azo-compounds. 

The  azo-compounds  are  red  or  yellowish-red  crystalline 
indifferent  substances  insoluble  in  water  but  soluble  in  alcohol, 
some  of  them,  e.g.  azo-benzene,  being  capable  of  distillation 


368     XXI.  DIAZO-  AND  AZO-COMPOUNDS  ;  HYDRAZINES. 


without  change.  Oxidizing  agents  convert  them  into  azoxy-, 
and  reducing  agents  into-  hydrazo-  or  amido-compounds. 
Chlorine  and  bromine  act  as  substituents. 

The  so-called  "mixed"  azo- compounds,  which  contain  a  benzene 
radicle  and  an  alcoholic  radicle  of  the  fatty  series,  are  also  known,  e.g. 
Azo-phenyl-ethyl,  CgHg— N=N— CgHg,  a  bright  yellow  oil. 

Modes  of  formation.  1.  By  the  cautious  reduction  of  nitro- 
or  azoxy-compounds,  e.g.  by  means  of  sodium  amalgam,  an 
alkaline  solution  of  stannous  oxide  (B.  18,  2912),  etc. 

2.  By  distilling  azoxy-benzene  with  iron  filings. 

3.  By  the  oxidation  of  hydrazo-benzene. 

4.  By  the  oxidation  of  amido-compounds,  e.g.  together  with 
azoxy-compounds  by  means  of  KMn04  • 

2CeH,.NH2  +  02  =  C^H  — N-N— C,H,  + 

5.  By  the  action  of  nitroso-  upon  amido-compounds.  In  this  way 
azo-benzene  is  obtained  from  nitroso-benzene  and  aniline  acetate  : 


Azo-benzene,  CgHg— N=N"— CgH^  (Mitscherlich,  1834), 
crystallizes  in  beautiful  large  red  plates ;  M.  Pt.  66°,  B.  Pt. 
293°. 

Azo-toluenes,  C6H4(CH3)— N=N— C6H4(CH3).    All  three  are  known. 

4.  Amido-azo-  and  Oxy-azo- compounds. 

Amido-groups  or  hydroxyls  are  capable  of  entering  into 
azo-benzene  etc.,  whereby  amido-  and  oxy-azo-benzenes  are 
formed,  thus : 

fiH-N=N-CeH,(NH,)  fiH,-N=N-CeH,(OH). 

Y  ^  ^  y 

Amido-azo-benzene.  Oxy-azo-benzene. 
The  former  are  at  the  same  time  bases  and  azo-compounds, 
and  the  latter  azo-compounds  and  phenols  {i.e.  weak  acids,  cf. 
p.  376). 


AMIDO-AZO-  AND  OXY-AZO-COMPOUNDS. 


369 


Formation,  1.  Amido-azo-benzene  is  obtained  from  azo- 
benzene  by  first  nitrating  it  and  then  reducing  the  resulting 
mononitro-azo-benzene. 

2.  Oxy-azo-benzene  results  from  azoxy-benzene  by  warming  it  with 
concentrated  sulphuric  acid,  (cf.  p.  367). 

3.  Amido-azo-compounds  are  also  formed  by  the  molecular 
rearrangement  of  the  diazo-amido-compounds,  according  to  p. 
365,  i.e.  in  a  manner  indirectly  by  the  action  of  diazo-benzene 
etc.  upon  primary  or  secondary  amines. 

4.  The  corresponding  amido-compounds,  whose  amido- 
hydrogen  is  substituted,  result  directly  from  the  action  of  diazo- 
compounds  upon  tertiary  amines,  (cf.  p.  363).  With  m- 
diamines,  the  diazo-compounds  yield  diamido-azo-benzenes  : 

CeH,.N=N.Cl+CeH,(NH2)2  =  CeH,N=N-CeH3.(NH,),  +  HCl. 

^  ,  ' 

Chrysoidin. 

Oxy-azo-compounds  result  in  an  analogous  manner  by  the 
action  of  diazo-compounds  upon  phenols  : 

CgH^N^N.Cl  +  CgH^OK  =  CgH^N^-N— CgH^OH  +  KGl. 

Reactions  of  this  kind  take  place  especially  with  resorcin 
and  the  phenols  of  the  naphthalene  series  (p.  466). 

The  amido-  and  oxy-azo-compounds  are  yellow,  red  or  brown 
in  colour  and  crystalline,  and  are  mostly  insoluble  in  water  but 
moderately  soluble  in  alcohol.  They  possess  the  character  of 
dyes  (azo-dyes),  the  chromogenic  character  of  the  azo-benzene 
being  developed  by  the  entrance  of  the  salt-forming  groups 
NH2  etc.  or  of  OH  (cf.  p.  24).  Thus  faintly  acid  solutions  of 
amido-azo-benzene  colour  wool  and  silk  a  beautiful  yellow 
("Aniline  yellow"),  and  Chrysoidin,  G-^^^^^,  HCl,  is  an 
orange-red  dye.  To  this  class  also  belongs  Vesuvine  or 
Bismarck  brown  (see  below). 

Instead  of  these  compounds  themselves,  their  sulphonic 
acids  (p.  376)  are  generally  used  as  dyes  ;  thus  the  so-called 
"  fast  yellow  "  ("  Echtgelb  ")  is  the  sodium  salt  of  amido-azo- 
benzene-sulphonic  acid. 

The  dyes  which  are  derivatives  of  amido-azo-benzene  are  termed 
( 506  )  2  A 


370     XXI.  DIAZO-  AND  AZO-COMPOUNDS  ;  HYDRAZINES. 


Chrysoidines,  and  those  which  are  derivatives  of  oxy-azo-benzene, 

Tropceolines. 

Of  especial  importance  are  those  azo-dyes  which  contain  a  naphthalene 
radicle  in  the  molecule.  They  are  formed  in  a  manner  exactly  analogous 
to  the  compounds  mentioned  above,  the  two  naphthylamines,  CioH^.NHg, 
and  the  a-  and  /3-naphthola,  C10H7.OH,  possessing  respectively  complete 
aminic  and  phenolic  characters,  and  their  sulphonic  acids  being  very 
active  chemically.  They  dye  yellow,  orange,  red,  brown,  violet  and 
even  blue.  Worthy  of  special  mention  is  Orange  II.,  C6H4(S03Na)— N 
=N — CioH(j(OH),  which  is  obtained  from  diazo-benzene-sulphonic  acid 
and  /3-naphthol. 

The  amido-group  in  amido-azo-benzene  may  be  diazotized,  as  given 
above,  and  the  resulting  diazo-compound  is  now  capable — like  diazo- 
benzene  chloride — of  yielding  azo-compounds  with  amines  or  phenols, 
Dis-azo-  (tetrazo-)  compounds,  as  they  are  termed,  (B.  15,  25) ;  e.g. 
CgHg— N=N-C6H4— N=N— C6H4.OH,  (B.  9,  628).  Many  of  the  most 
valuable  azo-dyes,  such  as  Biebrich  scarlet,  Crocein  scarlet  etc.  are 
derivatives  of  such  diazo-compounds. 

Tris-azo- compounds  also  exist,  (B.  16,  2028). 

In  the  formation  of  azo-dyes  of  this  nature,  the  azo-group 
always  takes  up  the  para-position  to  the  amidogen  or  hydroxy! 
if  possible.  Should  this  be  already  occupied,  it  goes  into  the 
ortho-position.  This  point  is  elucidated  by  the  examination 
of  the  decomposition  products  which  result  upon  reduction. 
The  azo-dyes  are  broken  up  at  the  point  of  the  double  bond 
by  tin  and  hydrochloric  acid  and  by  sulphide  of  ammonium, 
two  amido -compounds  resulting,  thus  : 

C6H5-N=N-C6H4N(CH3)2-f2H2  =  C6H5NH2-l-C6H4(NH2)-N(CH3)2. 

The  chemical  nature  of  an  azo-dye  is  thus  often  easily  arrived  at  by 
investigating  these  decomposition  products.  Upon  this  reaction  also 
depends  the  method  of  introducing  new  amido-groups  into  amines  and 
phenols,  mentioned  on  p.  349. 

For  the  nomenclature  of  the  azo-compounds,  see  B.  13,  2023. 


Amido-azo-benzene,  CgHg— N=N— CgH^.NHg  (1 863). 
Beautiful  yellow  plates  or  needles.  The  hydrochloric  acid 
salt  crystallizes  in  dark  violet  needles  and  yields  a  red 
solution. 


METHYL  ORANGE  ;  BISMARCK  BROWN. 


371 


Amido  azo-benzene-sulphonic  acid  (see  p.  376)  is  prepared 
by  sulphurating  amido-azo-benzene,  or  by  the  combination  of 
diazo-benzene-sulphonic  acid  with  aniline : 
C6H4(S03H)— N=N-C1  +  C^H^NH^ 

=  C6H,{S03H)— N=N— CgH^— (NH2)  +  HCl. 
It  has  a  flesh  colour,  it»  salts  being  yellow.    The  Di-sul- 
phonic  acid  crystallizes  in  glittering  violet  needles  and  its 
salts  are  likewise  yellow. 

Dimethyl-amido-azo-benzene,  CgHg — — C6H4.N(  0113)2.  Golden 
yellow  plates.  The  chloride  crystallizes  in  violet  needles.  Its  mono- 
sulphonic  acid,  methyl  orange,  helianthin,  or  Orange  III.,  is  used 
instead  of  litmus  as  a  delicate  indicator  in  alkalimetrical  titrations, 
its  yellow  solution  being  coloured  red  by  traces  of  acids ;  it  is  not 
affected  either  by  CO2  or  HgS,  (B.  18,  3290).  It  yields  amido- 
dimethyl-aniline  and  sulphanilic  acid  upon  reduction. 

Diamido-azo-benzene  or  chryso'idiney  CeHg— N"=N — C6H3.(NH2)2, 
(Caro,  Witty  1875) ;  the  chloride  crystallizes  in  large  octahedra,  built 
one  upon  the  other. 

Triamido-azo-beiizene,  Bismarck  hrown^ 

CeH,(NH2)-N=N-CeH3(NH2)2 
{Caro,  Griess,  1866),  is  produced  by  the  action  of  NgOg  upon 
m-phenylene-diamine,  one  half  of  the  latter  being  partially 
diazotized  to  CgH4(NH2) — N=N.C1  and  then  acting  on  the 
other  half,  as  given  at  p.  363.  It  forms  brownish-yellow 
crystals,  readily  soluble  in  hot  water;  the  salts  are  reddish- 
brown. 

Amido-azo- toluene,  from  diazo-p-amido-toluene,  has  the  constitution 

C6H4(CH3)-N=:N-C6H3(CH3)(NH2),  (B.  17,  77).  It  crystallizes  in 
orange-red  needles.  The  alcoholic  solution  is  turned  green  by  hydro- 
chloric acid. 

Oxy-azo-benzene,  CgHg— N=N— C6H4(OH)  {Griess,  1866), 
results  from  the  action  of  diazo-benzene  chloride  upon  phenol 
and  also  from  the  molecular  transformation  of  azoxy-benzene, 
(c£  p.  367).  It  crystallizes  in  brick-red  rhombic  prisms  and 
is  a  yellowish-red  dye. 

Dioxy-azo-benzene-sulphonic  acid,  C(5H4(S03lI)— N=N— C(jH3(OH)2, 
from  diazo-benzene-sulphonic  acid  and  resorcin,  forms  as  sodium  salt 
Chrysoin  or  Tropa3olin  O. 


372     XXI.  DIAZO-  AND  AZO-COMPOUNDS  ;  HYDRAZINES. 


Orange  II.,  (cf.  p.  370).  The  Ponceaux  and  Bordeaux  of  commerce 
are  mostly  prepared  from  the  xylidines  and  cumidines. 

Biebrich  scarlet,  C6H4(S03Na)-N=N— CgH^— N=N— CioHg.OH, 
(see  p.  370). 

D.  Hydrazines. 

The  hydrazines  of  the  benzene  series  {E,  Fischer)  entirely 
correspond  with  those  of  the  fatty,  (cf.  p.  117) : 

CgH^-NH-NH,    (CeH5)2N-NH,  (CoH5)(C,H5)N-NH,. 

Phenyl-hydrazine.     Diphenyl-hydrazine.  Phenyl-ethyl-hydrazine. 

Hydrazo-benzene  results  from  the  entrance  of  phenyl  into  the  second 
amidogen  of  phenyl-hydrazine. 


Phenyl-hydrazine,  C^^H^ — NH — NHg,  forms  a  colourless 
crystalline  mass,  melting  at  23°  to  a  colourless  oil  which 
quickly  becomes  brown  from  oxidation,  and  which  boils  at 
233°  without  decomposition.  It  combines  with  hydrochloric 
acid  to  the  chloride,  CgH^NgHg,  HCl  (plates).  Like  all 
hydrazines  it  is  characterized  by  strong  reducing  power, 
reducing  Fehling^s  solution  even  in  the  cold.  It  is  readily 
destroyed  by  oxidation  but  is  stable  towards  reducing  agents ; 
gentle  oxidation  of  the  sulphate  by  means  of  HgO  converts  it 
into  diazo-benzene  sulphate.  Conversely,  phenyl-hydrazine  is 
prepared:  (a)  By  reducing  diazo-benzene  chloride  with  the 
calculated  quantity  of  SnClg  and  HCl,  (F,  Meyer  and  Lecco, 
B.  16,  2976) : 

CeHg— N=N.C1  +  2H2  =  CeH^— NH— NH2,  HCl. 

(b)  By  reducing  diazo-benzene  potassium  sulphite, 
CgH^— N=N.S03K  (from  C6H5N2CI  and  K2SO3),  with  zinc 
dust  and  acetic  acid  to  phenyl-hydrazine  potassium  sulphite, 
CgHg — NH — NH.SO3K,  which  is  then  broken  up  into  phenyl- 
hydrazine  and  sulphuric  acid  upon  heating  with  HCl : 

CfiH^— NH-NH— SO3K  +  HCl  +  H^O 

=  CgH^— NH— NH2,  HCl  +  SO^KH, 


HYDRAZINES;  BENZENE-SULPHONIC  ACID.  373 


By  the  action  of  halogen-alkyl  upon  phenyl-hydrazine,  the  imido- 
hydrogen  atom  of  the  latter  is  replaced  by  alkyl ;  the  further  action  of 
halogen-alkyl  gives  rise  at  once  to  ammonium  compounds,  without 
replacement  of  the  hydrogen  of  the  amido-group.  Acid  radicles  may 
replace  either  one  or  two  H-atoms. 

The  base  is  an  important  and  often  an  exceedingly  delicate 
reagent  for  aldehydes  and  ketones,  combining  with  them  to 
hydrazones  with  elimination  of  water,  (cf.  pp.  135  and  143; 
also  B.  17,  572 ;  21,  984).  Most  of  these  compounds  are 
solid  and  crystalline  and  are  therefore  eminently  suited 
for  the  recognition  of  aldehydes  and  ketones,  and  also  of 
glucoses.  Phenyl-hydrazine  reacts  in  the  first  instance  with 
the  latter  in  the  same  way  as  it  does  with  the  former,  but 
here  (as  also  in  the  case  of  other  aldehyde-  and  ketone- 
alcohols)  a  second  hydrazine  molecule  may  come  into  play, 
whereby  ozazones  (p.  287)  result.  By  the  reduction  of  the 
hydrazones,  primary  amines  are  formed,  (B.  19,  1924)  : 


With  aceto-acetic  ether,  phenyl-hydrazine  forms  pyrazole 
derivatives  (see  antipyrine).  It  also  reacts  with  lactones, 
(B.  19,  1706). 

Phenyl-hydrazine-sulphonic  acid,  (B.  18,  2193).  Is  used  for  the 
preparation  of  tartrazine  (p.  245). 

Diphenyl-hydrazine,  (C6Hg)2N— NHg,  is  an  oily  base  which  boils 
without  decomposition  and,  like  phenyl-hydrazine,  is  easily  oxidized ; 
it  only  reduces  Fehling's  solution,  however,  when  warmed.  It  is 
obtained  by  reducing  diphenyl-nitrosamine,  (C6Hg)2N — NO,  with  zinc 
dust  and  acetic  acid ;  mercuric  oxide  converts  it  into  a  tetrazone. 
(Cf.  p.  118.) 


The  aromatic  sulphonic  acids  are  very  similar  in  properties 
to  the  sulphonic  acids  of  the  fatty  series. 

Benzene-sulphonic  acid,  C(3H^.S03H  (Mitscherlich,  1834), 
results  upon  warming  benzene  with  concentrated  sulphuric 
acid  (see  p.  306) : 


XXII.  AROMATIC  SULPHONIC  ACIDS. 


374 


XXII.  AROMATIC  SULPHONIC  ACIDS. 


As  in  the  case  of  ethyl-sulphuric  acid,  advantage  is  taken  of  the 
solubility  of  its  barium,  calcium  or  lead  salt  to  separate  it  from  the 
excess  of  sulphuric  acid. 

Small  tables  (  +  l^H^O),  deliquescent  in  the  air  and  readily 
soluble  in  alcohol.  The  barium  salt  crystallizes  in  glancing 
mother-of-pearl  plates. 

Behaviour.  1.  Benzene-sulphonic  acid  is  very  stable,  not 
being  decomposed  when  boiled  with  alkalies  or  acids,  as  ethyl- 
sulphuric  acid  is.  It  is,  however,  broken  up  into  benzene  and 
sulphuric  acid  when  heated  with  hydrochloric  acid  to  150°,  or 
with  water  vapour  at  a  high  temperature  (cf.  p.  325) : 

CeH,.S03H  -\-  H^O  =  CeH,  +  SO.H^. 

2.  When  fused  with  alkali,  it  yields  phenol : 

CeHg.SOgK  +  KOH  =  CgH^.OH  +  BO,K^. 

3.  When  it  is  distilled  with  potassium  cyanide,  benzo-nitrile 
is  formed  : 

CgHg-SOgK  4-  CNK  =  CoHg.CN  +  SOgKg. 

4.  When  it  is  acted  upon  by  PCI5,  its  chloride,  Benzene- 
sulphonic  chloride,  results : 

CeH^.SOgOH  +  PCI5  =  CeH^.SO^Cl  +  POCI3  +  HCl. 

The  latter  is  an  oil,  insoluble  in  water  and  solidifying  at  0° ;  as  an 
acid  chloride  it  is  reconverted  into  sulphonic  acid  by  hot  water,  and 
into  Benzene-sulphonamide,  CeHg.SOo.NHg  (glancing  mother-of-pearl 
sublimable  plates),  by  ammonia.  This  compound  corresponds  with  other 
amides  in  its  properties. 

5.  When  benzene-sulphonic  chloride  is  treated  with  zinc  dust, 
benzene-sulphinate  of  zinc  is  formed  : 

2CfiH5.S02Cl  +  2Zn  =  (C6H5S02)2Zn  +  ZnClg. 

Benzene-sulphinic  acid  crystallizes  in  large  glancing  prisms,  readily 
soluble  in  hot  water,  alcohol  and  ether.  It  possesses  reducing  properties 
and  is  itself  converted  into  thio-phenol  by  nascent  hydrogen  : 

CeHg.SOgH  +  2H2  =  CeHgSH  +  SHgO. 

The  sulphone,  Sulpho-benzide,  (CgH5)2S02,  results  from  the  action  of 
SO3  upon  benzene,  and  also  from  the  oxidation  of  phenyl  sulphide, 
(CeHgjgS.    It  crystallizes  in  plates,  is  only  sparingly  soluble  in  water 


SUBSTITUTED  BENZENE-SULPHONIC  ACIDS.  375 


but  more  readily  in  alcohol,  and  distils  unchanged.  In  properties  it 
is  analogous  to  diethyl-sulphone.  Mixed  sulphones  are  also  known, 
e.g.  Phenyl-ethyl-sulphone,  (C6H5)(C2H5)S02. 

Isomeric  with  the  sulphones  are  the  (easily  decomposable)  ethers  of 
benzene-sulphinic  acid,  e.g.  CgHg.SOglCaHg). 

Substitution  may  be  effected  in  benzene-sulphonic  acid  by 
chlorine,  bromine,  and  the  groups  NOg  and  NHg. 

The  Nitro-benzene-sulphonic  acids,  C6H4(]Sr02).S03H,  result  upon 
nitrating  benzene-sulphonic  acid  or  upon  sulphurating  nitro-benzene, 
the  m-compound  preponderating.    Reduction  converts  them  into  the  : 

Amido-benzene-sulphonic  acids,  C(3H4(NH2).S03H.  The 
^-compound,  which  is  termed  Sulphanilic  acid,  is  obtained  by 
heating  aniline  with  fuming  sulphuric  acid,  or  from  aniline 
sulphate  at  180°  to  200°  {Gerliardt,  1845);  also  by  reducing 
p-nitro-benzene-sulphonic  acid.  It  forms  rhombic  plates 
(  +  H2O),  rather  difficultly  soluble  in  water,  which  weather 
in  the  air. 

It  combines  with  bases,  e.g.  with  soda  to  sodium  sulphanilate, 
C6H4NH2S03Na  +  2H2O  (large  plates),   but  not  with  acids.  The 

formula  CgH4<^  SO.^-^  possibly  expresses  the  constitution  of  sulphanilic 

acid.  The  m-acid,  also  termed  Metanilic  acid,  is  employed  in  the 
preparation  of  the  azo-dye,  metaniline  yellow ;  it  crystallizes  in  fine 
needles  or  prisms. 

Diazo-benzene-sulphonic  acid,  CgH4<^^^''^^  (the  an- 
hydride  of  C^6H5<CgQ~^*^'^^,  IS  obtained   by  adding  a 

mixture  of  sulphanilate  and  nitrite  of  sodium  to  dilute 
sulphuric  acid.  White  needles,  sparingly  soluble  in  water. 
It  shows  all  the  reactions  of  the  diazo-compounds  and  is  of 
great  importance  for  the  preparation  of  azo-dyes  (p.  369). 

Benzene -disulphonic  acids,  C6H4(S03H)2  (principally  nieta-),  and 
Benzene -trisulphonic  acids,  C(}H3(S03H)3,  result  from  the  energetic 
sulphuration  of  benzene.  The  former  exist,  of  course,  in  three  isomeric 
modifications.  When  they  are  distilled  with  KCN,  they  yield  the  com- 
pounds CgH4(CN)2,  the  nitriles  of  the  phthalic  acids  ;  when  fused  with 
KOH,  they  all  go  into  resorcin  (m-dioxy-benzcne),  C(jH4(OH)2. 

A  Di-sulphanilic  acid,  CgH3(NH2)( 86311)2,  has  also  been  prepared. 


376 


XXIII.  PHENOLS. 


Almost  all  the  homologues  of  benzene,  with  the  exception  of  hexd,* 
methyl-,  etc.,  benzene,  are  likewise  capable  of  yielding  sulphonic  acids. 
From  toluene  are  obtained  the  Toluene -sulphonic  acids,  C6H4(CH3)S03H, 
which — as  di-derivatives — exist  in  three  different  modifications.  Of 
these  it  is  the  p-a>cid  which  is  formed  in  largest  quantity  directly  ;  its 
potassium  salt  crystallizes  beautifully. 

The  sulphonic  acids  of  the  three  xylenes,  the  Xylene -sulphonic  acids, 
C6H3(CH3)2S03H,  serve  for  the  separation  of  these  isomers  from  each 
other ;  and  the  power  of  crystallization  of  the  salts  or  amides  of  the 
sulphonic  acids  of  the  higher  benzene  homologues  is  frequently  made 
use  of  for  the  recognition  and  separation  of  these  hydrocarbons. 

As  an  example  of  a  complicated  aromatic  sulphonic  acid 
may  be  mentioned  (?-Bromo-m-nitro-|?-toluene-sulphonic  acid, 
CeH,(CH3)Br(NO,)(S03H). 

The  above  instance  is  sufficient  to  show  that  sulphonic  acids  may  be 
obtained  from  the  most  complicated  aromatic  compounds.  This  is  of 
especial  importance  if  the  latter  are  dyes  whose  application  is  hindered 
by  their  insolubility  in  water  or  by  other  circumstances,  as  in  the  case 
e.g.  of  indigo,  amido-azo-benzene,  etc.  ;  the  sodium  salts  of  their 
sulphonic  acids  are  for  the  most  part  readily  soluble  in  water,  without 
the  dye-character  becoming  weakened  thereby. 

For  sulphonic  acids  of  the  azo-dyes,  see  p.  370. 


XXIII.  PHENOLS. 

Phenols  are  oxygenated  derivatives  of  benzene  which  stand 
midway  in  chemical  character  between  alcohols  and  acids. 
^  They  are  derived  from  the  benzene  hydrocarbons  in  the  same 
way  as  the  alcohols  of  the  fatty  series  are  from  the  paraffins, 
i.e.  by  the  replacement  of  hydrogen  in  the  benzene  nucleus  by 
hydroxyl. 

The  phenols  are  either  liquid  or  solid  compounds  and  are 
often  characterized  by  a  peculiar  odour,  e.g.  carbolic  acid  and 
thymol.  Most  of  them  can  be  distilled  without  decomposition 
and  are  readily  soluble  in  alcohol  and  ether;  some  dissolve 
easily  in  water,  others  with  more  difficulty.  Many  of  them 
are  antiseptics,  e.g.  phenol,  creosol  and  resorcin. 


Phenols  ;  Behaviour.  377 


Summary  of  the  most  important  Phenols, 


Monatomic  : 

Diatomic  : 

Triatomic  : 

CgHg.OH 

Phenol  [41°]  (183°) 

C6H4(CH3).OH 
Cresols 
0- :        m- :        p- : 

[31°]  (188°)  [3°]  (201°)  [36°]  (198°) 

C6H4(OH)2 

Dioxy-benzenes 

0  —  Pyrocatechin 

[104°]  (245°) 

m  =  Resorcin  [118°]  (276°) 

7)=:Hydroquinone  [169°] 

LQuinoneJ 

Trioxy-benzenes 

v  =  Pyrogallol[115°]  (210°) 
a  =  Oxy-hydroquinone 
s  =  Phloroglucin  (217°) 

C6H,(CH3)(OH)3 
IVTethyl-pyrogallol 

C6H3(CH3)2.0H 

Xylenols 
e.g.  [74°]  (2ir) 

Cg,  ^/'-Cumenols 

Cjo,  Durenols 

CeH3(CH3)(C3H7).OH 
Thymol  [50°]  (222°) 
Carvacrol  [0°]  (237°) 

Tetratomic : 

aHo(CHo)(OH)o 
l:3:5  =  Orcm[86°]  (288°) 
1 :3 :4  =  Homo-pyro- 

catechin 

CeH,(0H)4 
Tetroxy-benzene 

Hexatomic : 

Cg,  Xylorcin,  etc. 

Hexoxy -benzene 

Cn,  Penta-methyl-phenol 

Cg,  Mesorcin 

Behaviour,  1.  The  phenols  behave  like  alcohols  in  that 
they  are  capable  of  forming  ethers  such  as  anisol,  CgHg.O.CHg, 
saponifiable  ethers  such  as  phenyl-sulphonic  acid,  CeHg.O.SOgH, 
thio-compounds,  etc. 

They  can  only  be  compared  with  the  tertiary  alcohols,  since  they 
cannot,  like  the  primary  or  secondary,  yield  acids  or  ketones  containing 
an  equal  number  of  carbon  atoms  in  the  molecule  upon  oxidation. 

Unlike  the  alcohols,  however,  the  phenols  are  very  stable  as 
regards  oxidizing  agents,  undergoing  only  substitution  and 
not  oxidation  by  halogens  and  nitric  acid,  and  not  going  into 
hydrocarbons  with  elimination  of  water,  etc. 

2.  The  phenols  possess  the  character  of  weak  acids;  they 
form  salts  with  alkalies,  etc.,  most  of  which  are  readily  soluble 
in  water,  and  which  correspond  with  the  alcoholates  but  are 
far  more  stable  than  these.  Thus,  the  phenols  dissolve  in 
the  alkalies  to  salts;   the  latter  are  usually  decomposed, 


378 


XXIII.  PHENOLS. 


however,  by  carbonic  acid.  The  acid  character  of  the  phenols 
is  considerably  increased  by  the  entrance  of  negative  groups, 
especially  NOg,  into  the  molecule.    (See  picric  acid.) 

3.  The  phenols  are  true  derivatives  of  benzene.  They  are 
capable  of  yielding  all  those  varieties  of  derivatives  which 
have  been  described  as  derivatives  of  benzene,  e,g,  chloro-, 
bromo-,  nitro-,  amido-,  diazo-  and  sulpho-phenols.  The  ease 
with  which  chlorine,  bromine,  nitric  acid,  etc.,  produce  such 
derivatives  is  characteristic  of  the  phenols  ;  thus  the  former 
substitute  even  in  very  dilute  aqueous  solution,  and  nitro- 
phenols  also  result  from  the  action  of  dilute  HNO3,  the 
concentrated  acid  giving  rise  at  the  same  time  to  di-  and 
trinitro-compounds. 

From  the  phenols  having  the  character  of  weak  acids,  it  follows  that 
the  group  CgHg  (phenyl)  is  of  a  negative  nature,  i,e.  that  it  acts  as  an 
acid  radicle. 

Occurrence,  Many  individual  phenols  are  found  in  the 
vegetable  and  animal  kingdoms. 

Constitution.  The  hydroxy  1  in  phenol,  CgH^.OH,  and  in  the 
dioxy-  and  trioxy-benzenes,  etc.,  containing  six  carbon  atoms,  is 
linked  to  the  benzene  nucleus.  That  this  is  also  the  case 
in  the  homologues  of  those  compounds  follows :  {a)  from  their 
completely  analogous  reactions  ;  (b)  from  their  behaviour  upon 
oxidation.  The  products  which  hereby  result  from  the  trans- 
formation of  the  side  chains  into  carboxyl  are  oxy-acids,  i.e., 
still  contain  the  hydroxyl. 

The  entrance  of  the  hydroxyl  into  the  side  chain  of  the 
benzene  homologues  is  also  theoretically  possible,  but  in  this 
case  it  is  not  phenols  which  result  but  true  aromatic  alcohols, 
(cf.  p.  395). 

A.  Monatomic  Phenols. 

Modes  of  formation.  1.  Many  phenols  result  from  the 
destructive  distillation  of  the  more  complex  carbon  com- 
pounds, especially  of  wood  and  coal;  they  are  therefore 
present  in  wood  and  coal  tars.    The  latter  contains  especially 


MONATOMIC  PHENOLS;  FORMATION. 


379 


plienol  and  its  homologues,  cresol,  etc. ;  the  former,  among 
other  products,  the  methyl  ethers  of  polyatomic  phenols, 
e.g.  guaiacol,  CeH4.(OH)(O.CH3),  and  its  homologue  creosol, 
CeH3.CH3(OH)(O.CH3). 

The  phenols  are  isolated  from  coal  tar  etc.  by  shaking  up  with 
potash,  in  which  they  dissolve,  saturating  the  solution  with  hydro- 
chloric acid,  and  purifying  the  precipitated  phenols  by  fractional 
distillation. 

2.  The  phenols  result  together  with  a  sulphite  upon  fusion 
of  the  sulphonic  acids  with  potash  or  soda,  {Kekule,  Wurtz, 
Dusart,  1867): 

CgH^.SOgK  +  2K0H  =  CgHg.OK  +  SO3K2  +  H^O. 

In  the  laboratory  silver  basins  are  used  for  this  fusion,  and  on  the 
large  scale  iron  boilers,  etc.  The  same  dioxy-benzene,  resorcin,  results 
from  all  three  benzene-disulphonic  acids.  The  chlorinated  sulphonic 
acids  and  the  chlorinated  phenols  also  exchange  the  halogen  for 
hydroxyl  upon  fusion  with  potash  : 

C6H4.C1(S03K)  +  4K0H  =  C6H4(OK)2  +  SO3K2  +  KCl  +  2H2O. 

3.  By  boiling  the  diazo-compounds  with  water  (Griess ;  cf. 
p.  362).  In  this  case  a  very  dilute  sulphuric  acid  solution  is 
employed : 

CeH^CKNiN.Cl)  +  H^O  =  Ce'H^CKOH)  +  N2  +  HCl. 

4.  Phenol  is  produced  from  benzene  by  the  action  of  ozone  or 
hydrogen  peroxide,  and  also  by  that  of  the  oxygen  of  the  air  in  presence 
of  caustic  soda  solution  or  of  aluminium  chloride.  In  an  analogous 
manner  di-  and  even  tri-oxy-benzene  may  be  obtained  by  fusing  phenol 
with  potash  : 

CA.OH  +  O  =  CeH^COH)^. 

5.  The  phenols  cannot  be  prepared  from  chloro-,  bromo-  or  iodo- 
benzene  as  the  alcohols  can  from  chloro-,  bromo-  or  iodo-alkyl,  the 
halogen  being  bound  too  firmly  to  the  benzene  nucleus.  If,  however, 
nitro-groups  are  present  at  the  same  time,  an  exchange  of  this  kind 
can  be  effected  by  heating  with  potash  or  soda  solution ;  trinitro- 
chloro-benzene  indeed  reacts  with  water  alone  : 

C6H,C1.(N02)3  +  HOH  =  CcH,(OH)(N02)3  +  HCl. 

6.  Similarly  the  amido-group  in  amido-compounds  may  be  replaced 
by  hydroxyl  upon  boiling  with  alkalies,  provided  nitro-groups  are 


380 


XXIII.  PHENOLS. 


also  present ;  thus  o-  and  p-  (not  m-)  dinitro-aniline  yield  dinitro- 
phenols,  a  reaction  which  corresponds  with  the  saponification  of  the 
amides,  (cf.  p.  318). 

7.  Phenols  result  from  the  dry  distillation  of  the  salts  of  the 
aromatic  oxy-acids  with  lime,  or  from  that  of  their  silver 
salts,  e,g, 

Gallic  acid.  Pyrogallol. 

8.  Homologues  of  the  phenols  are  produced  by  heating  phenol  with 
alcohols  and  zinc  chloride,  e.g.  ethyl  and  butyl  phenols,  (B.  14,  1845 ; 
15,  150). 

9.  Phenols  also  result  from  the  putrefaction  of  albumen, 
especially  j^-cresol,  Q>^^{G}1^011, 

Behaviour,  1,  2,  and  3.  For  the  alcoholic  and  acid  characters 
of  the  phenols  and  for  their  substitution,  see  above  and  also 
on  p.  383.  Bromine  water  precipitates  even  very  dilute  aqueous 
solutions  of  phenol,  with  the  formation  of  tribromo-phenol. 

4.  Many  phenols  give  characteristic  colourations  with  ferric 
chloride  in  neutral  solution,  e.g.  phenol  and  resorcin  violet, 
pyro-catechin  green,  and  orcin  blue-violet ;  while  pyrogallol 
yields  a  blue  colour  with  ferrous  sulphate  containing  a  ferric 
salt,  and  a  red  one  with  ferric  chloride.  Chloride  of  lime  and 
iodine  also  sometimes  give  particular  colourations. 

5.  When  the  phenols  are  mixed  with  concentrated  H2SO4  and  some 
NaNOg,  they  yield  intensively  coloured  solutions  which  turn  to  king's 
blue  on  saturation  with  potash,  (the  Liehermann  reaction,  p.  354). 

6.  The  sodium  and  potassium  salts  of  the  phenols  react  with 
CO2  (Kolbe)  or  with  COCI2,  with  formation  of  aromatic  oxy- 
acids,  e.g.  salicylic  acid : 

CgH^.OH  +  CO2  =  C6H4(OH).C02H. 

The  oxy-acids  are  also  formed  when  CCI4  and  NaOH  are 
used,  (B.  9,  1285),  and  their  aldehydes  by  the  action  of 
CHCI3  and  NaOH  upon  phenol,  (B.  9,  824). 

7.  The  phenols  combine  with  diazo-compounds  to  form  azo-dyes 
(p.  363);  when  heated  with  benzo-trichloride,  CeHg.feCla,  they  yield 
yellow-red  dyes  (see  aurin),  and  with  phthalic  acid,  the  phthaleius. 


PHENOL  OR  CARBOLIC  ACID. 


381 


8.  When  heated  with  zinc  dust,  the  phenols  are  converted 
into  the  corresponding  hydrocarbons,  (Baeyer) : 

CgHg.OH  +  H2  =  C^Hg  +  H2O. 

9.  Upon  heating  with  zinc-  or  calcium  chloride  and  ammonia,  the 
OH  is  replaced  by  NHg,  (cf.  p  343 ;  also  B.  19,  2901). 

10.  Heating  with  PCI5  partially  converts  the  phenols  into  chlorinated 
hydrocarbons,  and  heating  with  PgSg  into  thio-phenols  (p.  383). 


Phenol, 

Phenol,  carbolic  acid,  phenyl  alcohol,  CgH^OH.  Discovered 
in  1834  by  Runge  in  coal  tar.  Occurs  in  the  urine  of  the 
herbivora  and  in  human  urine  as  phenyl-sulphuric  acid,  in 
castoreum  and  in  bone  oil.  It  forms  a  colourless  crystalline 
mass  consisting  of  long  needles.  M.  Pt.  41°;  B.  Pt.  183°; 
Sp.  Gr.  at  0°,  1-084.  It  is  soluble  in  15  parts  of  water  at 
16°,  and  itself  dissolves  some  water,  a  small  percentage  of  the 
latter  sufficing  to  liquify  the  crystalline  phenol ;  alcohol  and 
ether  dissolve  it  readily.  It  is  hygroscopic  and  acquires  a 
reddish  colour  in  the  air,  possesses  a  characteristic  odour  and 
burning  taste,  is  poisonous,  and  acts  as  a  splendid  antiseptic. 
It  exerts  a  strongly  corrosive  action  upon  the  skin.  Soluble 
in  caustic  potash  but  not  in  the  carbonate.  Ferric  chloride 
colours  the  aqueous  solution  violet,  while  a  pine  shaving 
which  has  been  moistened  with  hydrochloric  is  turned  purple- 
red  by  phenol. 

Phenol-potassium,  CgHg.OK,  results  upon  heating  phenol  with  KOH. 
It  crystallizes  in  white  needles  which  are  readily  soluble  in  water  and 
which  redden  in  the  air. 

Phenol-calcium  or  carbolate  of  lime,  (CgHg.OjgCa,  is  employed  as  a 
disinfectant. 

For  the  reactions  of  phenol  and  its  homologues,  see  B,  14,  2306; 
16,  1207. 


382  XXIII.  PHENOLS. 


Summary  of  the  most  important  derivatives  of  Phenol, 


Substitution  Products. 

Ethers. 

Compound  ethers. 

C6H4(0H)C1 
(3)  Chloro-phenols. 
p-  :  [141°]  (217°) 

C6H4(OH).N02 
(3)  Nitro-phenols. 
[45°]  (214°);  ^- :  [114°] 

C6H2(OH)(N02)3 
Trinitro-phenols.  [e.g.  123°] 

C6H4(OH).NH2 
(3)  Amido-phenols. 
0- :  [170°] ;  p- :  [184°] 

C6H4(OH).S03H 
(3)  Phenol-sulphonic  acids. 

C«H,.0(CH3) 
Anisol. 
Liq.  (152°) 

Phenetol. 
Liq.  (172°) 

Diphenyl  ether.  [28°](246°) 

C6H4(NH2).OCH3 
(3)  Anisidines. 
p- :  [56°]  (245°) 

CeH3(NH2)(OCH3)(S03H) 
Anisidine-sulphonic  acid. 

QH5.0(S0.3H) 
Phenyl-SLilphuric 
acid. 

C5H5.0(aH,0) 
Acetyl-pheiiol. 
(190°) 

Thio-compounds. 

CgHg.SH 

Thio-phenol. 
(172°) 

Phenyl  sulphide. 
(272°) 

Ethers, 

Anisol  or  phenyl-methyl  ether,  CgH5.0(CH3),  and  Phenetol 
or  phenyl-ethyl  ether,  CgH5.0(C2H5),  are  best  got  by  heating 
phenol-potassium  (or  phenol  and  caustic  potash)  with  methyl 
or  ethyl  iodide  in  alcoholic  solution : 

CeHg.OK  +  CH3I  =  G,'R,.0(C}I^)  +  KI ; 

the  former  is  also  obtained  by  distilling  anisic  acid  with  lime. 
They  are  liquids  of  ethereal  odour  which  boil  at  a  lower 
temperature  than  phenol,  just  as  ether  boils  at  a  lower  one 
than  alcohol.  As  regards  behaviour,  they  are  very  stable 
neutral  compounds  of  hydrocarbon  character;  when  heated 
with  HI  to  140°,  or  with  HCl  to  a  higher  temperature,  they  are 
decomposed  backwards,  thus : 

CgH^.O.CHs  +  HCl  =  CeH^.OH  +  CH3CI. 

Phenyl  ether,  di-phenyl  oxide,  (C6Hg)20,  is  formed  upon  heating 
phenol  with  ZnClg  or  AlaClg,  but  not  with  H2SO4.  Long  needles.  Not 
split  up  by  HI. 


PHENYL-»ULPHURIC  ACID;  THIO-PHENOLS. 


383 


Compound  ethers  of  Phenol 

Phenol  reacts  as  an  alcohol  with  inorganic  and  organic  acids 
to  form  compound  ethers. 

Phenyl-sulphuric  acid  (also  termed  phenol-sulphuric  acid), 
0^^^.0(S0^}1),  is  only  capable  of  existence  in  the  form  of 
salts,  being  immediately  saponified  into  phenol  and  sulphuric 
acid  when  attempts  are  made  to  isolate  it.  The  potassium 
salt,  CgH5.0.(S03K)  (plates,  sparingly  soluble  in  water),  is 
found  in  the  urine  of  the  herbivora  and  also  in  human  urine 
after  the  consumption  of  phenol,  and  it  may  be  prepared 
synthetically  by  heating  phenol-potassium  with  potassic  pyro- 
sulphate  in  aqueous  solution,  (Baumann).  It  is  very  stable 
towards  alkalies,  but  is  saponified  by  hydrochloric  acid. 

The  other  phenol-sulphuric  acids,  e.g.  cresol-sulphuric  acid,  which 
occur  in  urine,  are  exactly  analogous  to  the  above. 

Phenol-cartoonic  ether,  phenyl  carbonate,  CO(O.C6Hg)2,  is  prepared 
from  COCI2  and  CeHgONa.  It  crystallizes  in  glancing  needles,  M.  Pt. 
78°,  and  is  convertible  into  salicylic  acid. 

Sodium  phenyl- carbonate,  CgHg.  0.  COgNa,  results  from  CO2  and 
CgHg.ONa,  and  goes  into  sodium  salicylate  upon  heating.  Acids  decom- 
pose it  into  CO2  and  phenol. 

Acetyl-phenol,  0^1150.031130,  obtained  from  phenol-sodium 
and  acetyl  chloride,  or  from  phenol,  acetic  acid  and  sodium 
acetate,  is  an  easily  saponifiable  liquid  which  boils  at  190°. 

Thio-phenols. 

Thio-phenol,  phenyl  hydrosulphide,  OgHg.SH,  is  prepared 
from  benzene-sulphonic  chloride,  OgHg — SOgOl,  as  given  at  p. 
374,  or  by  heating  phenol  with  P2S5.  It  is  a  liquid  of  most 
unpleasant  odour  and  of  pronounced  mercaptan  character  (see 
p.  94). 

It  yields,  for  instance,  a  mercury  compound,  (C6HgS)2Hg,  crystalliz- 
ing in  glancing  needles,  and  also  salts  with  other  metals.  When 
warmed  with  concentrated  H28O4,  a  cherry-red  and  then  a  blue  colour- 
ation is  produced.    It  is  readily  oxidizable  to  phenyl  disulphide. 


384 


XXIII.  PHENOLS. 


Closely  related  to  the  above  are  Phenyl  sulphide,  (0^115)28, 
a  liquid  smelling  of  leeks  and  oxidizable  to  Phenyl  sulphone, 
(^6115)2802;  and  Phenyl  disulphide,  (CgH5)2S2  (glancing 
needles,  M.  Pt.  60°),  which  is  very  easily  prepared  by  the 
action  of  iodine  upon  the  potassium  compound  of  thio-phenol, 
or  by  exposing  an  ammoniacal  solution  of  the  latter  to  the  air. 
It  is  readily  reducible  to  thio-phenol,  and  is  indirectly  oxidiz- 
able to  Benzene  di-sulph-oxide,  (6(3115)28202.  (Cf.  the  corre- 
sponding compounds  of  the  fatty  series,  pp.  93  et  seq,) 

Chloro-  and  Bromo-phenols, 

When  chlorine  is  led  into  phenol,  0-  and  ^-Chloro-phenols 
are  formed.  These  also  result,  together  with  the  m-compound, 
by  reducing  and  diazotizing  the  haloid-nitro-benzenes. 

Of  the  isomeric  bi-derivatives,  the  ^^-compounds  have  the  highest 
melthig  point  and  the  0-  the  lowest ;  thus  o-chloro-  and  bromo-phenols 
are  liquid  and  the  p-compounds  solid.  When  fused  with  caustic  potash 
they  yield  dioxy-benzenes  (p.  388),  often  with  a  molecular  rearrange- 
ment. The  chloro-phenols  have  a  sharp  persistent  odour.  All  the  five 
hydrogen  atoms  of  phenol  have  been  replaced  by  chlorine  and  bromine. 

Nitroso-phenols, 

As  Nitroso-phenol,  CgH4(0H)(N0),  (1:4),  is  designated 
the  compound  prepared  from  phenol  and  nitrous  acid  {Baeyer, 
B.  8,  816),  or  by  boiling  nitroso-dimethyl-aniline  with  caustic 
soda  solution  (see  p.  354) : 

C6H4(NO).N(CH3)2  +  NaOH  =  CeH4(N0).0Na  NH(CH3)2. 

It  crystallizes  in  fine  colourless  needles  which  readily  become 
brown,  or  in  large  greenish-brown  plates. 

It  yields  a  soda  salt  crystallizing  in  red  needles  and  amorphous  dark 
coloured  salts  with  the  heavy  metals.  Potassic  ferricyanide  in  alkaline 
solution  oxidizes  it  to  p-nitro-phenol,  while  tin  and  hydrochloric  acid 
reduce  it  to  ^-amido-phenol.  It  gives  the  Liebermann  reaction  with 
phenol  and  concentrated  sulphuric  acid.  Since,  however,  it  is  also 
formed  from  quinone  and  hydroxylamine  hydrochloride,  according  to 
the  equation ; 


NITRO-PHENOLS  ;  PICRIC  ACID.  385 
CgHA  +  NH2OH   =   C6H4(NO)OH  +  H2O, 

N(OH) 

its  constitution  is  probably  expressed  by  the  formula  C6H4<:^  | 

0 

(cf.  B.  17,  213,  801).  According  to  this  it  is  an  oxime  of  quinone,  in 
agreement  with  which  stands  the  fact  of  its  being  further  convertible 
by  hydroxylamine  into  quinone  di-oxime  (p.  394). 


Nitro-phenols. 

On  mixing  phenol  with  cold  dilute  nitric  acid,  0-  and  p-nitro- 
phenols  are  formed,  the  latter  preponderating  if  the  liquid  is 
cold,  and  the  former  if  it  is  warm.  Upon  distilling  with 
steam,  the  1  :  2  compound  (strongly  smelling  yellow  prisms) 
volatilizes,  while  the  1  :  4  (colourless  tables)  remains  behind. 
For  their  formation,  see  also  pp.  378  and  353.  97i-Nitro- 
phenol  results  from  m-nitraniline  by  diazotizing  the  latter. 

The  acid  character  of  phenol  is  so  strengthened  by  the  entrance  of 
the  nitro-group  that  its  salts  are  not  decomposed  by  COg  but  result 
from  the  nitro-phenols  and  alkaline  carbonate.  o-Nitro-phenol- sodium, 
CgH4(N02)ONa,  crystallizes  in  dark  red  prisms,  and  p-Nitro-phenol- 
potassium  in  golden  needles.  Halogens  and  nitric  acid  readily  substi- 
tute further  in  these  (or  in  phenol  itself),  yielding  two  isomeric  Dinitro- 
phenols,  C6H3(N02)20H,  (OH  :  NOg  :  NOg  =  1  :  2  :  4  and  1:2:6,  i.e. 
the  two  NOg-groups  are  always  in  the  ?7Z -position).  Further  nitration 
gives  : 

Picric  acid,  trinifro-phenol,  CgH2(N02)3.0H,  (OHiNOgi 
NO2  :  NO2  =  1:2:4:6).  This  compound  was  discovered  in 
1799.  It  may  also  be  prepared  by  the  direct  oxidation  of 
5-trinitro-benzene  with  KgFeCyg,  and  is  produced  by  the  action 
of  concentrated  nitric  acid  upon  the  most  various  organic  sub- 
stances, e.g.  silk,  leather,  wool,  resins  and  aniline.  It  is  a 
strong  acid  and  forms  beautifully  crystallizing  salts  which 
explode  violently  upon  heating  or  when  struck.  Very  spar- 
ingly soluble  in  water.  Crystallizes  from  alcohol  or  water  in 
yellow  plates  or  prisms,  M.  Pt.  122  5°.  Can  be  sublimed 
without  decomposition,  but  is  explosive  also.  It  is  an  import- 
ant yellow  dye. 

Picryl  chloride,  C6H2(N02)3C1  (from  picric  acid  and  PCI5),  resembles 
(506) 


386 


XXIII.  PHENOLS. 


the  acid  chlorides  (p.  318)  in  behaviour.  Picric  acid  forms  beautifully 
crystallizing  addition-compounds  with  many  hydrocarboUvS,  e.(j.  CeHg, 
CjoHg,  etc.  With  KCN  it  yields  Iso-purpuric  acid,  CgHgNuOg,  whose 
potassium  salt  dyes  a  garnet-brown  like  orchilla. 

Isomers  of  picric  acid  are  also  known. 

Amido-phenols. 

The  nitro-phenols  go  into  amido-phenols  upon  reduction : 

C6H4(OH)NH2  C6H3(OH)(NH2)2  C6H3(OH)N02(NH2)  C6H2(OH)(NH2)3. 

0-,  m-,  p-  Di-amido-  Nitro-amido-  Tri-amido- 

Amido-phenols.      phenols.  phenols.  phenol. 

In  the  Amido-phenols  {Hofmann^  1857)  the  acid  character  of 
the  phenols  is  neutralized  by  the  presence  of  the  amido-groups, 
so  that  they  only  yield  salts  with  acids;  but,  as  phenols,  they 
are  still  capable  of  yielding  derivatives  (see  anisidine),  while 
on  the  other  hand  their  amido-hydrogen  is  exchangeable  in 
the  most  various  ways,  as  in  the  case  of  aniline,  but  chiefly 
for  acid  radicles. 

The  acid  derivatives  of  the  o-Amido-phenols  yield,  like  the  o-diamines, 

so-called  anhydro-bases,  e.g.  methenyl-o-amido-phenol,  C6H4<^q^CH, 

which  may  also  be  prepared  directly  by  the  action  of  the  acid  in 
question,  e.g.  formic  acid,  upon  the  amido-phenols,  (cf.  p.  349). 

The  Hydrochlorides  of  the  amido-phenols  are  relatively  stable  in  the 
air  and  often  capable  of  sublimation,  the  free  bases  (colourless  plates) 
being  on  the  other  hand  very  readily  oxidized  in  the  air,  with  blacken- 
ing and  the  formation  of  resin,  especially  if  they  are  impure.  ^^-Amido- 
phenol  is  easily  oxidized  to  quinone,  C6H4O2,  by  potassic  bichromate 
and  sulphuric  acid,  while  chloride  of  lime  converts  it  into  quinone  chlor- 
imide,  C6H40(NC1) ;  with  HgS  and  FegCle,  compounds  of  the  methylene- 
blue  group  result  (p.  355).  Amido-thio-phenols,  C6H4(SH)NH2,  are  also 
known,  of  which  the  o-compound  is  again  characterized  by  the  ready 
formation  of  anhydro-compounds,  such  as  Methenyl-amido-thio-phenol, 

C6H4<^'^^CH,  isomeric  with  phenyl  isothiocyanate  {Hofmann^  B.  13, 

1226). 

From  the  amido-phenols  are  further  derived  Diazo-phenols 
and  Azo-phenols. 

The  Anisidines,  amido-anisols,  methoxy -anilines^  C6H4(O.CH3).NH2, 


HOMOLOGUES  OF  PHENOL. 


387 


are  bases  similar  to  aniline,  and  are  used  in  the  colour  industry, 
(azo-dyes). 

The  Oxy-diphenylamines,  e.g.  CgHg— NH— C6H4.OH,  are  phenylated 
amido-phenols,  and  react  accordingly  (see  also  p.  356). 

Phenol-sulphonic  acids,  CgH4(OH)(S03H).  The  0-  and  p- 
acids  are  obtained  from  phenol  and  concentrated  H2SO4  at  a 
moderate  temperature,  that  is,  with  much  greater  ease  than 
the  benzene-sulphonic  acids ;  the  ortho-acid  changes  into  the 
para-  on  warming,  even  when  in  aqueous  solution.  The 
m-compound  can  be  prepared  indirectly  by  fusing  m-benzene- 
disulphonic  acid  with  potash.    All  three  are  crystalline. 

The  0-  and  m-acids  yield  0-  and  m-dioxy-benzenes  when  fused  with 
KOH,  but  the  ^^-acid  does  not  react  in  this  way,  being  attacked  only 
at  temperatures  over  320°,  and  no  resorcin  then  resulting ;  the  same 
applies  to  caustic  soda.  o-Phenol-sulphonic  acid  is  used  as  an  antiseptic 
under  the  name  of     Aseptol,"  (B.  18,  Kef.  506). 

Phenol-di-  and  tri-sulphonic  acids  are  also  known. 

Homologues  of  Phenol, 

The  homologues  of  phenol  resemble  the  latter  very  closely 
in  most  of  their  properties,  form  perfectly  analogous  deriva- 
tives, and  possess  likewise  a  disinfectant  action  and  a  peculiar 
odour  (the  cresols  an  unpleasant  fsecal-like  odour,  the  higher 
homologues  one  which  is  less  marked). 

They  differ  from  phenol  mainly  by  the  presence  of  side 
chains  which,  as  in  the  case  of  toluene  etc.,  may  undergo  certain 
transformations.  In  especial,  when  they  are  used  in  the  form  of 
alkyl  or  acetyl  derivatives  or  sulphonic  acids,  they  can  be 
oxidized  in  such  a  manner  that  the  side  chains  (methyl  groups) 
are  transformed  into  carboxyl,  with  the  production  of  oxy- 
carboxylic  acids.  The  cresols  themselves  cannot  be  oxidized 
even  by  chromic  acid  mixture,  but  are  completely  destroyed 
by  permanganate  of  potash. 

Negative  substituents,  especially  if  they  are  present  in  the  o-position, 
render  such  oxidation  more  difficult  in  acid,  but  facilitate  it  in  alkaline 
solution. 

The  Cresols,  G^^{GI[,^OIL,  are  all  three  present  in  coal 


388 


XXIII.  PHENOL&. 


tar  and  are  also  contained  in  the  tar  from  pine  and  beech 
wood.  o-Cresyl-sulphuric  acid  (analogous  to  phenyl-sulphuric 
acid)  is  found  in  the  urine  of  horses,  and  the  ^-compound  in 
human  urine. 

^-Cresol,  G^fl^(GI{^)OIi,  is  produced  by  the  decay  of 
albumen.  Its  dinitro-compound  is  a  golden-yellow  dye  which 
is  used  as  ammonium  or  potassium  salt  under  the  name  of 
Victoria  orange. 

Thymol,  CioHi40,(CH3:C3H^:OH  =  1:4:3)  is  found  together 
with  cymene,  C^qH^^,  and  thymene,  CioH^g,  in  oil  of  thyme, 
Thymus  Serpyllum,  and  is  used  as  an  antiseptic. 

m-Xylenol,  CgHisO,  (CHg  :  CHg :  OH  =  1:3:4)  is  found  in  the 
creosote  of  beech-wood  tar. 

Carvacrol,  C10H14O,  (CgHg :  C3H7 :  OH  =  1:4:2)  present  in  Origanum 
hirtum,  is  prepared  either  by  heating  camphor  with  iodine  or  from 
its  isomer,  car  vol,  and  vitreous  phosphoric  acid.  Carvol,  C10H14O,  the 
chief  constituent  of  oil  of  cumin  (from  Carvum  Carvi),  appears  to  be 
a  keto-dihydro-cymol,  (B.  19,  12). 

For  other  homologues  of  phenol,  see  table,  p.  377 ;  Ethyl-,  Propyl- 
and  Butyl -phenols  and  also  Penta-methyl-phenol  (B.  18,  1825)  have 
likewise  been  prepared. 

B.  Diatomic  Phenols. 

By  the  entrance  of  two  hydroxyls  into  benzene  and  its 
homologues,  the  diatomic  phenols  are  produced.  These  are 
analogous  to  the  monatomic  compounds  in  most  of  their 
relations,  but  differ  from  them  in  the  same  way  as  the 
diatomic  alcohols  do  from  the  monatomic.  They  are  likewise 
formed  by  methods  completely  analogous  to  those  for  the 
monatomic  phenols,  especially  by  fusion  with  potash  (p.  374) ; 
instead,  however,  of  the  compound  expected,  an  isomeride 
which  is  stable  at  that  high  temperature  frequently  results 
(see  resorcin).  The  ^-dioxy-compounds  are  characterized  by 
their  close  connection  with  the  quinones.  Many  of  the  poly- 
atomic phenols  are  strong  reducing  agents. 

Pyro-catechin,  CgH4(OH)2  (1:2),  which  was  first  obtained 
by  the  distillation  of  catechin  (Mimosa  Catechu),  is  present  in 


PYRO-CATECHIN  ;  RESORCIN  ;  HYDROQUINONE.  389 


raw  beet  sugar  and  results  from  the  fusion  of  many  of  the 
resins  as  well  as  of  o-phenol-sulphonic  acid  with  potash.  It 
crystallizes  in  short  white  rhombic  prisms,  which  can  be 
sublimed,  and  are  readily  soluble  in  water,  alcohol  and  ether. 

It  is  prepared  by  heating  its  mono-methyl  ether,  Guaiacol, 
C6H4(OH)(O.CH3),  a  constituent  of  beech-wood  tar,  with  hydriodic 
acid  (see  anisol,  p.  382).  Like  most  of  the  polyatomic  phenols  it  is 
very  unstable  in  an  alkaline  solution,  which  quickly  becomes  green 
and  then  black  in  the  air.  The  aqueous  solution  is  coloured  green  by 
Fe2Cl6  and  then  violet  by  NHg  (reactions  of  the  o-dioxy-compounds). 
It  possesses  reducing  properties,  causing  separation  of  the  metal  from 
a  solution  of  silver  nitrate  even  in  the  cold.  By  boiling  it  with  potash 
and  potassic  methyl-sulphate,  it  may  be  reconverted  into  guaiacol, 
which  likewise  shows  the  ferric  chloride  reaction  and  possesses  reducing 
powers.    Veratrol,  C6H4(OCH3)2,  is  its  di-methyl  ether. 

Resorcin,  GoH^iOR)^,  (1:3)  {Hlasiwetz,  Earth,  1864),  is 
obtained  on  fusing  many  resins  (Galbanum,  Asafoetida),  also 
m-phenol-sulphonic  acid,  all  three  bromo-benzene-sulphonic 
acids,  and  m-  and  ^-benzene-disulphonic  acids  with  potash. 
The  last  mentioned  compounds  are  employed  for  its  prepara- 
tion on  the  technical  scale.  It  also  results  from  the  distillation 
of  the  extract  of  Brazil  wood.  White  rhombic  prisms  or  tables 
which  quickly  become  brown  in  the  air,  dissolve  easily  in 
water,  alcohol  and  ether,  and  reduce  an  aqueous  solution  of 
silver  nitrate  when  warmed  with  it,  and  an  alkaline  solution 
even  in  the  cold.  With  FegClg  resorcin  gives  a  dark  violet 
colouration. 

It  yields  dyes  with  NgOg.  When  heated  with  phthalic  anhydride  it 
is  converted  into  fluorescein  (see  eosin  ;  test  for  m-dioxy-benzenes),  and 
it  is  therefore  prepared  on  the  large  scale.  Diazo-compounds  transform 
it  into  azo-dyes,  (cf.  p.  369). 

Its  trinitro-derivative  is  Styphnic  acid,  06H(OH)2(N02)3,  which  is 
formed  by  the  action  of  nitric  acid  upon  many  gum-resins. 

Hydroquinone,  G^H^OTl)^  (1:4),  (mhler,  1844). 

Formation.  By  the  oxidation  of  quinic  acid,  C7II32O6,  by  means  of 
Pb02,  by  the  saponification  of  arbutin,  and  from  succino-succinic  ether 
as  given  at  p.  429,  etc. 

Preparation.    By  the  oxidation  of  aniline  with  chromic  acid 


390 


XXIII.  PHENOLS. 


mixture,  and  also  by  the  reduction  of  quinone  with  sulphur 
dioxide.  Small  monoclinic  plates  or  hexagonal  prisms,  of 
about  the  same  solubility  as  its  isomers  and  capable  of  being 
sublimed.  Ammonia  colours  it  reddish-brown,  while  chromic 
acid,  ferric  chloride  and  other  oxidizing  agents  convert  it  into 
quinone  and  eventually  into  quinhydrone  (p.  393). 

Acetate  of  lead  yields  a  white  precipitate  with  a  solution  of  pyro- 
catechiii,  but  none  with  resorcin,  while  hydroquinone  is  only  precipi- 
tated in  presence  of  ammonia.  From  the  observed  heat  of  neutraliza- 
tion, resorcin  and  hydroquinone  behave  towards  soda  as  dibasic  acids, 
and  pyrocatechin  as  a  weak  monobasic  acid. 

Dioxy-toluenes,  C6H3(CH3)(OH)2.  Among  the  various  isomerides 
which  have  been  prepared  (see  B.  15,  2995),  there  may  be  mentioned  : 

1.  Orcin,  (CHg  :  OH  :  OH  =  1:3:5),  which  is  found  in  many  lichens 
(Rocella  tinctoria,  Lecanora,  etc.).  It  results  from  orsellinic  acid  with 
separation  of  COg,  e.g,  upon  fusing  extract  of  aloes  with  potash,  and  it 
can  also  be  prepared  synthetically  from  toluene,  (B.  15,  2992).  Of 
especial  interest  is  its  synthesis  from  acetone-dicarboxylic  ether  (p.  244) 
and  sodium,  (B.  19,  1446).  It  crystallizes  in  colourless  prisms  of 
sweetish  taste  which  tend  to  become  red,  and  whose  aqueous  solution  is 
coloured  blueish-violet  by  FcgClg.  It  does  not  yield  a  fluorescein  with 
phthalic  anhydride.  By  the  oxidation  of  its  ammoniacal  solution  in  the 
air,  orcein,  C7H7NO3,  the  chief  constituent  of  the  commercial  orchil 
dye,  is  formed,  a  compound  which  is  also  prepared  directly  from  the 
lichens  named  above.  Related  to  it  is  the  well  known  colouring  matter 
litmus. 

2.  Homo-pyrocatecliin,  C6H3(CH3)(OH)2,  (CH3 :  OH  :  OH  =  1:3:4), 
deserves  mention  on  account  of  its  mono -methyl  ether  Creosol, 
C6H3CH3(OH)(O.OH3),  occurring  in  beech- wood  tar.  Creosol  is  a  liquid 
similar  to  guaiacol,  boiling  at  220°,  and,  as  a  derivative  of  pyrocatechin, 
giving  a  green  colouration  with  FegClg. 

Among  the  other  isomers  are  Cresorcin,  Tolu-hydroquinone,  etc. 

Homologous  with  the  above  are  e.g.  Xylorcin  (CH3  :  CH3  :  OH  :  OH 
=  1:3:4:6)  and  Beta-orcinol  (wi-dioxy-p-xylene),  C6H2(CH3)2(OH)2  ; 
Mesorcin,  C6H(CH3)3(OH)2,  (CH3 :  CH3  :  CH3  :  OH  :  OH  =  1  :  3  :  5  :  2  : 4) 
(see  table,  p.  377) ;  Thymo-hydroquinone,  CioHi402,  which  is  present 
in  Arnica  montana,  etc. 

Eugenol,  C10H12O2,  =  C6H3(OH)(OCH3)(CH2.CH  :  CH2),  the  chief 
constituent  of  oil  of  cloves,  is  a  derivative  of  an  unsaturated  diatomic 
phenol. 


PYROGALLOL ;  PHLOROGLUCIN. 


391 


0.  Triatomic  Phenols. 

rPyrogallol  =  1:2:^  = 

C6H3(OH)3  j  Phloroglucin  =  1 :  3  :  5  =  s  h  ^"^ee  table,  p.  377. 

vOxy-hydroquinone  =  1:2:4  =  aJ 

1.  Pyrogallol,  pyrogallic  acid  (Scheele,  1786),  is  the  most 
important  of  these  three  isomers.  It  is  obtained,  apart  from 
synthetical  reactions,  by  heating  gallic  acid,  CO2  being  split 
off: 

CeH2(OH)3.CO,H  =  CeH3(OH)3  +  CO^. 

It  crystallizes  in  white  plates,  M.  Pt.  115°,  readily  soluble 
in  water  and  capable  of  subliming  without  decomposition.  It 
is  an  energetic  reducing  agent,  e.g.  for  silver  salts,  and  its 
alkaline  solution  rapidly  absorbs  oxygen  from  the  air,  hence  it 
is  used  in  gas  analysis,  as  a  developer  in  photography,  and  so 
on.  The  aqueous  solution  is  coloured  bluish-black  by  a 
solution  of  ferrous  sulphate  containing  ferric  salt,  and  purple- 
red  by  iodine. 

PyrogaUol  dimethyl  ether,  C6H3(OH)(OCH3)2  {Hofmann),  is  con- 
tained in  beech-wood  tar,  as  are  likewise  the  dimethyl  ethers  of  the 
compounds  C6H2(CH3)(OH)3  and  CgH2(C3H7)(OH)3,  homologous  with 
pyrogallol. 

2.  Phloroglucin,  (Hlasiwetz^  1855),  results  from  the  fusion 
of  various  resins  and  of  resorcin  with  potash  or  soda,  by  the 
action  of  alkali  upon  phloretin,  and  by  fusing  its  tricarboxylic 
ether  (whose  synthetical  formation  is  given  on  p.  321)  with 
potash.  Large  prisms  which  weather  in  the  air  and  sublime 
without  decomposition ;  M.  Pt.  218°.  Gives  with  FcgClg  a 
dark  violet  colouration. 

Its  reactions  partly  agree  with  the  formula  C6H3(OH)3,  e.g.  it  forms 
metallic  compounds  and  a  Tri-methyl  ether,  C6H3(0. €113)3,  insoluble  in 
alkali ;  but,  on  the  other  hand,  it  yields  like  the  ketones  a  Trioxime, 
CgHg(]S.0H)3,  and  therefore  appears  readily  to  build  up  the  atomic 
group  CH2— CO— CH2— CO— CH2— CO,   =  Tri-keto-hexa-methylene, 


which  is  termed  the  secondary  or  pseudo-iormy  in  contradistinction  to 
the  first-named  (the  tertiary).  (Cf.  pp.  317  and  265 ;  also  B.  19,  159, 
2186.) 


392 


XXIII.  THENOLS. 


3.  Oxy-hydroquinone  results  from  the  fusion  of  hydroquinone  with 
potash,  (B.  16,  1231).  Like  pyrogallol  it  does  not  react  with  liydroxyl- 
amine. 


D.  Tetra-,  penta-  and  hexatomic  phenols. 

Tetr-oxy-benzene,  CoH^iO}!)^  (1  :  2  :  4  :  5),  is  prepared  from  succino- 
succinic  ether,  (B.  19,  23S5).  It  crystallizes  in  yellow  needles  and  is 
stable  when  pure.  Its  chloro-derivative,  Dichloro-tetroxy-'benzene, 
C6Clo(OH)4,  is  readily  oxidizable  to  chloranilic  acid  (see  p.  394). 

Hex-oxy-benzene,  Cfi(OH)g,  forms  as  potassium  salt  the  so-called 
Potasshim  carhoxide,  CgOgKg.  It  crystallizes  in  colourless  readily 
oxidizable  prisms  and  can  be  converted  into  its  quinone  (tri-quinone), 
CeOg  (p.  395).  It  has  also  been  prepared  synthetically,  (B.  18,  499, 
1833). 

As  a  pentatomic  phenol  of  the  reduced  benzene,  CgH.{Hg)(0H)5,  is 
to  be  regarded  Quercite  (in  Quercus),  a  substance  which  resembles 
maunite  ;  and  as  a  hexatomic  phenol,  Phenose,  Cg.(Hg)(OH)g,  which  has 
been  prepared  by  treating  CgHg.  Clg  with  moist  oxide  of  silver. 


E.  Quinones. 

Quinone,  CgH^Og  (1838).  Quinone  is  produced  when 
chromic  acid  is  added  to  a  solution  of  hydroquinone.  It 
crystallizes  in  yellow  needles  or  prisms  of  a  characteristic 
pungent  odour  something  like  that  of  nut  shells,  sparingly 
soluble  in  water  but  readily  in  alcohol  and  ether,  and  capable 
of  sublimation;  M.  Pt.  116°.  Corresponding  to  it  we  have 
a  large  number  of  higher  homologues,  etc.  These  also  are 
solids  mostly  of  a  yellow  colour  and  volatile  with  steam  ;  they 
result  from  the  oxidation  of  the  corresponding  para-dioxy-com- 
pounds  or  of  the  higher  atomic  phenols,  which  contain  two 
hydroxyls  in  the  para-position. 

The  isomeric  dioxy-benzenes  do  not  show  this  formation  of 
quinone. 

Quinone  is  also  produced  by  the  oxidation  of  many  aniline 
and  phenol  derivatives  belonging  to  the  para-series,  e.g. 
p-amido-phenol,  sulphanilic  acid  and  jp-phenol-sulphonic  acid ; 
further,  by  the  oxidation  of  aniline  itself  by  means  of  chromic 


QUINONE. 


393 


acid,  (see  B.  19,  14G7).  It  was  first  obtained  by  distilling 
quinic  acid  with  manganese  dioxide  and  sulphuric  acid. 
Quinone  readily  volatilizes  with  steam,  but  at  the  same  time 
much  of  it  is  decomposed.  Exposure  to  light  causes  it  to  turn 
brown,  and  it  colours  the  skin  yellow-brown.  It  is  easily 
converted  into  hydroquinone  by  reducing  agents  such  as  SO2, 
HI,  SnClg  and  HCl  etc.,  and  can  therefore  act  as  an  oxidizer. 

Chlorine  and  bromine  act  upon  it  as  substituents,  while  hydrochloric 
acid  forms  Mono-chloro-hydroquinone  : 

C6H4O2  +  HCl  =  CgHgCUOHja. 

It  yields  sparingly  soluble  crystalline  compounds  with  primary 
amines  and  also  (coloured)  compounds  with  phenols.  It  is  soluble  in 
alkalies,  the  solution  decomposing  rapidly.  With  hydroquinone  it 
forms  an  addition-compound  termed  Quinhydrone,  CgH402  +  C6H4(OH)2, 
crystallizing  in  green  prisms  with  a  metallic  glance,  which  also  results 
as  an  intermediate  product  in  the  oxidation  of  hydroquinone  or  in  the 
reduction  of  quinone. 

Constitution,  Quinone  is  derived  from  benzene  by  the 
exchange  of  two  atoms  of  hydrogen  for  two  of  oxygen  which, 
from  the  close  connection  between  quinone  and  hydroquinone, 
must  be  in  the  ^-position.  The  constitution  of  quinone  may 
be  explained  either  by  assuming  that  these  two  oxygen  atoms 
are  linked  together  as  in  peroxide  of  hydrogen,  H — 0 — 0 — H? 
so  that  the  benzene  nucleus  remains  unchanged,  or  that  the 
latter  experiences  a  partial  reduction,  with  the  formation  of  a 
derivative  of  CgHg,  a    diketo-dihydro-benzene  "  : 


CO 

/O         HC/9\CH  ^0  HC/\CH 

C  CO 
According  to  the  first  of  these  two  formulae  quinone  would 
be  a  peroxide,  according  to  the  second,  a  ketone  (quinone 
CO 

=  C2H2<^QQ^C2ll2).    In  favour  of  the  latter  view  are  (1) 

the   fact   that   quinone  can  be  converted  into  an  oxime, 
C(N  OH 

C2H2<C    QQ    ^CgHg  (identical  with  nitroso-phenol,  p.  384), 


394 


XXIII.  PHENOLS. 


I 


and  into  a  dioxime,  Quinone  dioxime,  ^^2H2<Cc(N  011)^^2^2 

(B.  20,  613);  and  (2)  its  relations  to  the  analogously  consti- 
tuted anthraquinone.    (Cf.  B.  18,  568;  A.  223,  170.) 

The  formation  of  succino-succinic  ether,  which  was  spoken  of  on 
p.  321,  involves  a  synthesis  of  quinone.    The  acid  corresponding  to 
that  ether  is  a  dicarboxylic  acid  of  Quinone  tetrahydride  (^^-diketo- 
CH2.CO.CH2 

hexa-methylene),   \'        \\  =  C6H4O2  (p.  430) ;  it  can  be  trans- 

Cxl2.  CO.CH2 

formed  into  the  dicarboxylic  acid  of  hydroquinone,  C6H4(OH)2,  by  the 
elimination  of  two  atoms  of  hydrogen,  and  into  bromanil  (tetra-bromo- 
quinone)  by  bromine,  (cf.  A.  211,  306;  B.  16,  1412;  B.  19,  429, 
1977). 

Chlorinated,  etc.,  products  are  derived  from  hydroquinone  as  well 
as  from  quinone. 

Chloranil,  tetrachloro-quinone,  CgCl^Og,  which  crystallizes  in 
glancing  yellow  plates,  is  obtained  by  chlorinating  quinone 
and  also  by  oxidizing  many  organic  compounds,  e.g.  phenol, 
with  HCl  and  KCIO3.  It  goes  into  tetra-chloro-hydroquinone, 
a  colourless  compound,  upon  reduction,  and  acts  as  an  oxidizing 
agent,  converting  e.g.  dimethyl-aniline  into  a  methyl  violet. 
A  dilute  solution  of  potash  transforms  it  into  potassium 
chloranilate,  CgCl202(OK)2  +  HgO  (dark  red  needles),  cor- 
responding to  which  there  is  also  an  analogous  nitro-compound, 
potassium  nitranilate,  C(3(N02)202(OK)2.  The  latter  salt  is 
distinguished  by  its  sparing  solubility,  hence  its  formation 
may  be  made  use  of  as  a  test  for  potassium  compounds.  For 
its  constitution,  see  B.  19,  2398. 

Bromanil,  G^Brfi^^  and  Bromanilic  acid,  CgBr2(02)(OH)2, 
are  compounds  analogous  to  the  above. 

As  homologues  of  quinone  may  be  mentioned  Tolu-quinone, 
C6H3(02)(CH3),  Xylo-quinone,  CeH2(02)(CH3)2,  Thymo- 
quinone,  C,H2(02)(CH3)(C3H,),  etc. 

Several  of  these  can  be  prepared  synthetically  by  the  condensation 
of  1  :  2  di-ketones,  for  instance  di-acetyl  yields  xyloquinone  under  the 
influence  of  alkali,  (cf.  B.  21,  1411)  : 

CHo— CO— CO— CHH2  CH3— C— CO— CH 

+  HaCH— CO— CO-CH3  HC— CO— C— CHg 


QUINONE  CHLOR-IMIDES. 


395 


Dioxy-quinone,  CeH.(02)(OH)2,  which  corresponds  to  tetroxy -benzene 
(p.  392),  forms  small  brownish-black  crystals.  It  is  the  mother  sub- 
stance of  chlor-  and  nitranilic  acids,  mentioned  above. 

From  hexoxy-benzene  there  can  be  prepared  Tetroxy-qumone 
C  (0  )(OB.h  Dioxy-diquinoyl  or  rhodizonic  acid,  C6(02)(02)(OH)2,  and 
finally  Tri^uinoyl,  C,mmm  +  SIi,0.  In  both  the  latter  com- 
pounds  the  formation  of  quinone  has  taken  place  more  than  once,  (of. 
B.  18,  499,  1833). 

P.  Quinone  Ohlor-imides. 

Eelated  to  the  quinones  are  the  quinone  chlor-imides,  which 
result  from  the  oxidation  of  the  j?-aniido-phenols  or^^-phenylene- 
diamines  by  means  of  chloride  of  lime. 

Quinone  clilor-imide,  CeH4(0)(NCl),  results  from  HCl-^^-amido-phenol, 
and  quinone  dichlor-imide,  CeH^lNCl)^,  from  HCl-p-phenylene-diamme. 
The  first  named  crystaUizes  in  golden  yellow  crystals  which  are  volatile 
with  steam  ;  reduction  converts  it  into  amido-phenol,  and  boiling  with 
water  into  quinone,  the  dichloro-compound  behaving  in  an  analogous 
manner.  For  these  compounds  the  foUowing  constitutional  formulae  are 
assumed : 

O  /O  /NCI  ^^^^N.Cl 

^«^<kci      ^^''^<N.C1         ^«^^<NC1  ^^^<N.C1 

Quinone  chlor-imide.  Quinone  dichlor-imide. 

These  formulae  are  based  upon  the  fact  that  derivatives  of  diphenyl- 
amine  result  from  their  action  upon  phenols  or  amines.  (See  indo- 
phenols,  p.  356.) 


XXIV.  AROMATIC  ALCOHOLS,  ALDEHYDES 
AND  KETONES. 

A.  Aromatic  Alcohols, 

While  the  phenols  remind  us  of  the  tertiary  alcohols  of  the 
fatty  series  in  their  properties,  although  they  differ  from  these 
in  many  points,  we  are  acquainted  at  the  same  time  with  real 
aromatic  alcohols,  ie.  compounds  which  possess  the  alcoholic 
character  in  its  entirety.  The  most  important  of  these  is 
(primary)  benzyl  alcohol,  C^H^.OH,  which  is  isomeric  with 


396    XXIV.  AROMATIC  ALCOHOLS,  ALDEHYDES  AND  KETONES. 


the  cresols,  this  isomerism  being  explained  by  the  different 
position  of  the  hydroxyl  in  the  molecule ;  thus,  while  the 
cresols,  like  all  phenols,  contain  the  hydroxyl  linked  to  the 
benzene  nucleus,  it  is  present  in  the  side  chain  in  benzyl 
alcohol  : 

C6H4(CH3).OH,  Cresols;  CgH^— CHg-OH,  Benzyl  alcohol. 

This  follows  from  the  formation  of  benzyl  alcohol  from 
benzyl  chloride,  GqH.^ — CHgCl  (and  vice  versa)^  and  also  from 
the  fact  that  it  can  be  oxidized  to  an  aldehyde  and  an  acid 
containing  the  same  number  of  carbon  atoms  in  the  molecule 
as  itself,  these  being  likewise  mono-derivatives  of  benzene  : 

CgHs— CH2.OH         C.Hs— CHO  CgH^— CO.OH 

Benzyl  alcohol.  Benzaldehyde.  Benzoic  acid. 

Benzyl  alcohol  may  also  be  looked  upon  as  methyl  alcohol  in  which 
one  atom  of  hydrogen  is  replaced  by  the  group  CgHg  : 


Methyl  alcohol,  =  carbinol.  Benzyl  alcohol,  =  phenyl  carbinol. 

It  is  therefore  the  simplest  existing  aromatic  alcohol. 

Among  its  homologues  the  following  primary  and  secondary 
alcohols  may  be  mentioned  (tertiary  being  also  known) : 

C«Ha  .OH  CeH4(CH3)— CH2.OH        CgH^— CH^— CH^.OH 
Tolyl  alcohols.  and  C.Hg— CH(OH)— CH3 

Phenyl- ethyl  alcohols. 

C6E4(C3Hy)-CH2.0H     C6H5-CH2-CH2-CH2.  OH 

Cumic  alcohol  (p).  Phenyl-propyl  alcohol,  etc. 

Di-  and  triatomic  alcohols  likewise  exist ;  these  must  contain 
not  less  than  8  and  9  atoms  of  carbon  in  the  molecule  respec- 
tively (see  p.  189,  etc.),  e,g,  : 


C.H.(CH,.OH),,jCSri;iK.l. 

CeHg— CH(OH)— CH(OH)— CH2.  OH 


Phenyl-glycerine  (stycerine),  etc. 

All  these  ccfftipounds  are,  as  alcohols,  perfectly  analogous  to 


BENZYL  ALCOHOL. 


397 


the  alcohols  of  the  fatty  series,  so  far  as  regards  the  formation 
of  alcoholates,  ethers,  compound  ethers,  mercaptans,  amines, 
phosphines,  etc.  They  are  however  benzene  derivatives  at  the 
same  time,  and  consequently  yield  chloro-,  bromo-,  nitro-,  amido-, 
etc.,  substitution  products.  By  the  entrance  of  the  phenyl 
group  into  unsaturated  fatty  alcohols,  there  result  unsaturated 
aromatic  alcohols  which  resemble  the  unsaturated  compounds 
of  the  fatty  series  to  the  closest  extent  in  their  chemical 
behaviour,  but  are  at  the  same  time  benzene  derivatives. 

These  remarks  also  apply  in  full  degree,  mutatis  mutandis,  to 
the  aromatic  aldehydes  and  ketones  (see  below). 


Benzyl  alcohol,  OgH^ — CH2.OH,  is  a  colourless  liquid  of 
faint  aromatic  odour,  sparingly  soluble  in  water ;  B.  Pt.  206°. 
It  occurs  naturally  in  Peru  and  Tolu  balsams  as  benzoic  and 
cinnamic  ethers,  and  is  formed  from  benzyl  chloride  just  as 
alcohol  is  from  ethyl  chloride. 

Preparation.  By  the  reduction  of  its  aldehyde  or,  better,  by 
the  action  of  aqueous  potash  upon  the  latter,  whereby  the  one 
half  of  it  is  oxidized  and  the  other  half  reduced,  (B.  14,  2394): 

2CeH5^CHO  +  KOH   =  CeH^— CH^-OH  +  C.H^— COOK. 

Benzyl  hydrosulphide,  CgHg — CHg-SH,  the  corresponding  thio- 
alcohol,  is  a  liquid  of  most  unpleasant  odour  and  of  typical  mercaptanic 
character.  The  amine,  Benzylamine,  CgHg — CH2.NH2,  has  been  already 
referred  to  at  p.  359  ;  homologous  amines  are  also  known. 

Phenyl-methyl  carbinol,  C^Hg— CH(OH)— CH3,  B.  Pt.  203",  can  be 
prepa.red  by  reducing  acetophenone,  CgHg — CO — CH3  (p.  400),  into 
which  it  is  reconverted  by  gentle  oxidation. 

The  simplest  of  the  unsaturated  alcohols  in  Cinnamic  alcohol  or 
styrone,  CgHjoO,  =  CfjHg— CH=CH — CH2(0H),  which  occurs  as 
cinnamic  ether  styracin ")  in  storax.  It  crystallizes  in  glancing 
needles  of  hyacinth-like  odour,  and  goes  into  cinnamic  acid  when 
oxidized  gently,  and  into  benzoic  when  the  oxidation  is  more  vigorous. 
As  an  alcohol  it  forms  ethers,  etc. 


/ 


398    XXIV.  AROMATIC  ALCOHOLS,  ALDEHYDES  AND  KETONES. 


B.  Aromatic  Aldehydes. 

Benzoic  aldehyde,  benzaldehyde,  or  oil  of  bitter  almonds^ 
CoHr, — CHO.  Discovered  in  1803;  investigated  by  Zi^Ji^  and 
Wohler,  (A.  22,  1).  Colourless,  strongly  refracting  liquid  of 
agreeable  bitter  almond  oil  odour.  B.  Pt.  179°;  Sp.  Gr.  at 
15°,  1*05.  Readily  soluble  in  alcohol  and  ether,  but  only 
sparingly  in  water  (1  in  30). 

Modes  of  formation.  These  are  for  the  most  part  analogous 
to  those  of  the  fatty  aldehydes.    It  results  : 

(a)  From  the  oxidation  of  the  corresponding  alcohol. 
{h)  From  the  reduction  of  the  corresponding  acid  (distillation  of  a 
mixture  of  benzoate  and  formate  of  calcium). 

(c)  By  heating  the  corresponding  dichloride,  benzal  chloride, 
also  called  benzylene  dichloride,  CgH^ — CHClg  (from  toluene), 
with  water  or  sulphuric  acid,  or,  as  is  done  on  the  technical 
scale,  with  water  and  hydrate  of  lime ;  also  by  heating  benzyl 
chloride,  CgH^ — CHgCl,  with  water  and  lead  nitrate. 

(d)  Together  with  dextrose  and  hydrocyanic  acid  by  decom- 
posing amygdalin,  C2oH27NO|;^,  a  compound  which  occurs  in 
bitter  almonds  and  crystallizes  in  white  plates  (p.  512),  either 
by  means  of  sulphuric  acid  or  by  emulsin  (a  ferment  likewise 
present  in  bitter  almonds,  cf.  p.  294) : 

C2oH2^NOii  +  2H2O  =  CeH,— OHO  +  ^G^Tl^f^^  +  CNH. 

(e)  By  the  action  of  cromyl  chloride,  CrOaClg,  upon  toluene.  This  is 
the  Etard  reaction,  an  important  one  for  the  synthesis  of  aldehydes 
from  hydrocarbons,  (B.  17,  1462,  1700;  cf.  also  p.  327). 

Behaviour,  1.  Its  behaviour  is  that  of  an  aldehyde  in  every 
respect.  Thus  it  is :  {a)  easily  oxidizable  to  the  acid,  and  it 
reduces  an  ammoniacal  silver  solution  with  the  production  of 
a  mirror  ;  (h)  reducible  to  the  alcohol ;  (c)  capable  of  forming 
an  addition-compound  with  NaHSOg  (but  not  one  with  NH3, 
giving  in  the  latter  case  hydro-benzamide,  (CgH5CH)3N2,  with 
elimination  of  H2O) ;  {d)  capable  of  combining  with  HON  (see 
mandelic  acid) ;  {e)  condensible  with  other  aldehydes  and  also 
with  acids  and  ketones  of  the  fatty  series,  e.g.  to  cinnamic 


BENZALDEUYDE,  ETC. 


399 


acid,  (B.  14,  2460;  15,  2856);  also  with  dimethyl-aniline, 
phenols,  etc.  to  triphenyl-methane  derivatives ;  (/)  capable  of 
combining  with  hydroxylamine  and  phenyl-hydrazine  to 
benzaldoxime,  GqR^ — CH=N.OH,  and  benzaldehyde-phenyl- 
hydrazone,  CgH^ — CH^NgH — CgH^,  respectively  (a  delicate 
reaction,  cf.  B.  17,  574). 

2.  It  also  behaves  in  every  respect  like  a  benzene  derivative, 
in  that  it  is  capable  of  being  substituted  by  halogens 
(indirectly)  and  of  being  nitrated,  amidated,  sulphurated  etc. 
(directly). 

As  in  the  case  of  toluene,  chlorine  enters  the  side  chain  here  at  the 
boiling  temperature,  with  formation  of  benzoyl  chloride,  CqH^ — COCl. 

Of  its  derivatives  the  Nitro-benzaldehydes,  C6H4(N02)CHO,  are 
especially  worthy  of  mention.  The  m-compound  is  formed  in  largest 
proportion  upon  nitrating,  but  at  the  same  time  the  o-compound  to  the 
extent  of  20  p.c.  The  latter  can  be  best  prepared  by  oxidizing  o-nitro- 
cinnamic  acid  by  KMn04  in  presence  of  benzene,  (B.  17,  121).  Long 
colourless  needles,  M.  Pt.  46°.  It  is  particularly  interesting  on  account 
of  its  convertibility  into  indigo  by  means  of  acetone  and  caustic 
soda  (B.  15,  2856),  and  its  reducibility  to  o-Amido-benzaldehyde, 
C6H4(NH2)CHO,  a  compound  crystallizing  in  silvery  glancing  plates, 
M.  Pt.  40°,  which  is  of  value  for  various  synthetical  reactions.  (See 
quinoline;  also  B.  16,  1833.) 

Among  its  homologous  aldehydes  we  have  the  three  Toluic  aldehydes, 
C6H4(CH3) — CHO,  together  with  the  isomeric  Phenyl-acetic  aldehyde, 
CgHg — CHg — CHO ;  further,  Cumic  aldehyde,  cuminol,  or  isoproj)yl- 
bemaldehyde,  C6H4(C3H7) — CHO,  which  is  contained  in  Roman  oil  of 
cumin. 

As  an  example  of  a  diatomic  aldehyde,  Terephthalic  aldehyde, 
C6H4(CHO)2  (1:4),  may  be  taken. 

Cinnamic  aldehyde,  CgHg— CH=CH— CHO,  is  the  chief  constituent 
of  oil  of  cinnamon  (Persea  cinnammomum),  from  which  it  may  be 
isolated  by  means  of  its  NaHSOg-compound.  It  is  an  oil  of  aromatic 
odour  which  boils  at  247°  and  readily  distils  along  with  steam. 


0.  Aromatic  Ketones. 

Acetophenone,  CeH^— CO— CH3,  is  the  simplest  repre- 
sentative of  the  (mixed)  aromatic  ketones.  It  crystallizes  in 
colourless  plates,  readilysoluble  in  water,  M.  Pt.  20°,  B.  Pt.  200% 


400   XXIV.  AROMATIC  ALCOHOLS,  ALDEHYDES  AND  KETONES. 


and  is  obtained  by  the  normal  modes  of  preparation  for  ketones 
{e.g.  by  distilling  a  mixture  of  acetate  and  benzoate  of  calcium),  as 
also  by  the  conjoint  action  of  acetyl  chloride  and  aluminium 
chloride  upon  benzene.  It  unites  in  itself  the  properties  of  a 
ketone  of  the  fatty  series  and  of  a  benzene  derivative.  It 
yields  benzoic  acid  and  carbon  dioxide  upon  oxidation,  is  sub- 
stituted in  the  side  chain  by  halogens  when  heated  {e.g.  to 
Phenacyl  bromide,"  C^Hg—CO— CH2Br),  and  is  nitrated  by 
HNO3,  etc. 

Its  homologues  resemble  it  in  every  respect,  but  are  liquid  at  the 
ordinary  temperature. 

The  ketone  proper  of  benzoic  acid,  Benzophenone,  CeHg— CO — CgHg, 
is  described  on  p.  444. 

Aromatic  diketones  (cf.  p,  221)  have  also  been  prepared,  e.g. 
Benzoyl-acetone,  CgH^ — CO — CHg — CO— CH3,  and  Acetophenone -acetone, 
CgHg— CO— CH2— CH2— CO— CH3.  The  latter,  like  acetonyl-acetone, 
is  readily  converted  into  furfurane,  pyrrol  and  thiophene  derivatives  (see 
p.  299),  e.g.  into  phenyl-methyl-pyrrol,  C4H2(C6H5)(CH3).NH. 


D.  Oxy-alcohols  and  -aldehydes;  Ketone-alcohols. 

Summary, 

OH  Saligenin.  OH        Salicylic  aldehyde. 

CeHKg^JbsK    ^  alSl.       ^^^<Iko'  Anisaldehyde. 

^  TT  / nxT     /o\  =  Protocatechuic 

/OH        (4)  /OH  (4) 

CeH3^0CH3     (3)  =  CeH3^  OCH3  (3)  =  VaniUin. 

\CH2.0H(1)      aiconoi.  \CH0  (1) 

etc.,  etc. 

A  large  number  of  compounds  are  known  which  unite  in 
themselves  the  properties  of  a  phenol  and  of  an  alcohol  or 
aldehyde.  They  are  derived  from  the  simple  alcohols,  etc.  by 
the  entrance  of  hydroxyl  into  the  benzene  nucleus. 


VANILLIN. 


401 


Several  of  these  compounds  occur  in  nature,  e.g.  saligenin  is 
a  constituent  of  salicin  (see  the  glucosides),  while  salicylic 
aldehyde  is  found  in  spiraea  varieties  and  vanillin  in  the  vanilla 
capsules.  Anisaldehyde  results  from  the  oxidation  of  anisol 
(methyl  phenate). 

Oxy-aldehydes  are  formed  synthetically  by  the  action  of  chloroform 
upon  an  alkaline  solution  of  phenol,  of  dioxy-benzene,  of  monomethyl- 
dioxy -benzene,  etc. ;  e.g.  1:2-  and  1  :  4-oxy-benzaldehydes  from  phenol, 
protocatechuic  aldehyde  from  pyrocatechln,  and  vanillin  from  guaiacol. 
(See  p.  407,  4/.) 

Vanillin,  methyl-protocatechuic  aldehyde,  CgHgOg,  which  crys- 
tallizes in  beautiful  needles,  is  prepared  on  the  large  scale  from 
Coniferin,  CjgH220g  +  SHgO,  a  compound  occurring  in  the  sap  of 
the  cambium  in  the  coniferae.  This  is  broken  up  by  acids  into 
glucose  and  Coniferyl  alcohol,  C6H3(OH)(OCH3)(C3H4.0H), 
which  latter  goes  into  vanillin  upon  oxidation,  (Tiemann  and 
Haarmann).;  the  CHg-group  is  split  off  upon  heating  with 
hydrochloric  acid  to  200°,  with  the  formation  of  protocatechuic 
aldehyde.  Vanillin  is  also  found  e.g.  in  asparagus,  raw  beet 
sugar  and  asafoetida,  and  it  likewise  results  from  the  oxidation 
of  olive  wood,  etc. 

Benzoyl  carbinol,  oxy-acetophenone,  CgHg — CO— CH2.OH,  is  a  ketonic 
alcohol  which  can  be  prepared  from  the  bromide,  CgHg — CO — CHgBr, 
and  which  crystallizes  in  glancing  plates.  It  resembles  acetone-alcohol, 
although  it  is  more  stable  than  the  latter,  and  has  like  it  strongly 
reducing  properties,  reducing  alkaline  silver  and  copper  solutions  even 
in  the  cold.    It  yields  an  osazone  with  phenyl-hydrazine. 


XXV.  Aromatic  Acids. 

The  aromatic  acids  are  analogous  to  the  fatty  acids  in  most 
respects.  As  acids  they  are  capable  of  forming  exactly  the 
same  kinds  of  derivatives  as  the  latter,  i.e.  salts,  compound 
ethers,  chlorides,  anhydrides,  amides,  etc.,  e.g.  : 

CfjHg.CC^H,  Benzoic  acid. 
CgHg.COglCaHg),  Ethyl  benzoate  ;  (QjH^.  00)^0,  Benzoic  anhydride  ;  . 
CeHg.CO.Cl,  Benzoyl  chloride  ;      CeHg.CO.NH^,  Benzamide  ;  etc. 

But  they  are  at  the  same  time  benzene  derivatives  and,  as 
(506)  20 


402 


XXV.  AROMATIC  ACIDS. 


such,  can  undergo  most  of  the  transformations  of  which  benzene 
itself  is  capable.  Thus  chlorine,  bromine  and  iodine  substitu- 
tion products  and  nitro-,  amido-  and  sulphonic  acids,  etc.  can 
be  prepared  from  them,  the  amido-acids  can  be  diazotized,  and, 
upon  the  entrance  of  oxygen  into  the  benzene  nucleus,  there 
result  phenolic  acids  (i.e.  compounds  which  possess  the 
characters  of  phenols  and  of  acids),  quinone  acids,  (i.e.  com- 
pounds at  once  a  quinone  and  an  acid),  etc. 

Alcohol-acids,  ketone-acids,  etc.,  are  likewise  capable  of 
existence  in  the  aromatic  as  well  as  in  the  fatty  series. 

We  have,  for  instance,  the  following  derivatives  : 

C6H4CI.CO2H,  chloro-benzoic  acids ; 
C6H4(N02).  CO2H,  nitro-benzoic  acids  ; 
C6H4(NH2).002H,  amido-benzoic  acids; 
C6H4(S03H).C02H,  sulpho-benzoic  acids; 
C6H4(OH).C02H,  oxy-benzoic  acids  ; 
C6H5.CH(OH).C02H,  mandelic  acid,  etc. 

Their  modes  of  formation  are  likewise  partly  analogous  to 
those  of  the  fatty  acids^  (cf.  p.  404). 

The  homologous  acids  however  do  not  here  show  the  gradual  changes 
in  physical  properties  which  the  homologous  fatty  acids  do. 

Constitution.  Corresponding  to  the  aromatic  acids  there  are 
again  nitriles,  e.g.  to  benzoic  acid  benzo-nitrile,  CgHg.CN,  which 
ma}^  also  be  regarded  as  cyanogen  derivatives  of  the  hydro- 
carbons (in  the  above  case,  cyano-benzene),  and  which  are 
converted  into  the  acids  upon  saponification.  From  this  it 
follows  that  their  constitution  must  correspond  exactly  with 
that  of  the  fatty  acids ;  like  the  latter  they  are  characterized 
by  the  presence  of  carboxyl,  CO. OH,  in  the  molecule.  There 
are  monobasic,  di-,  tri-  and  up  to  hexabasic  aromatic  acids, 
according  to  the  number  of  hydrogen  atoms  in  the  molecule 
which  are  readily  replaceable  by  metal,  i.e.  according  to  the 
number  of  carboxyl-groups : 

CeH,(CO,H),  CeH3(C02H)3  C^iCO^H), 

Phthalic  acids.     Benzene-tri-carboxylic  acids.    Mellitic  acid. 
Unsaturated  aromatic  acids  also  exist  in  large  number. 
They  chiefly  differ  from  the  saturated  acids  in  that,  as  un- 


CONSTITUTION  ;  NOMENCLATURE. 


403 


saturated  compounds,  they  readily  form  addition-compounds 
with  Hg,  CI2,  HCl,  etc.,  going  thereby  into  the  saturated  acids 
or  their  substitution  products;  this  difference  is  thus  just  the 
same  as  that  between  the  unsaturated  and  saturated  acids  of 
the  fatty  series.  In  most  of  these  additi  >ns  the  benzene 
nucleus  remains  unaltered,  (cf.  p.  312,  3).  Their  constitution 
is  therefore  entirely  analogous  to  that  of  the  acids  of  the 
acrylic  or  propiolic  series ;  they  contain  a  side  chain  with  a 
double  or  triple  carbon  bond. 

The  oxy-acids,  such  as  the  oxy-benzoic  acids,  which  possess 
at  the  same  time  phenolic  and  acid  characters,  manifestly 
contain  phenol-hydroxyl  (i.e.  hydroxy  1  which  is  linked  directly 
to  the  benzene  nucleus)  in  addition  to  the  carboxyl  group  or 
groups ;  they  are  capable  of  yielding  salts  either  as  acids  or  as 
phenols,  but  otherwise  they  correspond  in  many  points  with 
the  alcohol-acids  of  the  fatty  series. 

The  true  aromatic  alcohol-acids,  such  as  mandelic  acid 
(phenyl-glycollic  acid),  which  completely  correspond  with  the 
latter,  manifestly  contain  their  alcoholic  hydroxyl  not  in  the 
benzene  nucleus  but  in  the  side  chain,  as  is  also  the  case  with 
the  aromatic  alcohols. 

Nomenclature.  The  most  rational  nomenclature  is  the  designa- 
tion of  the  aromatic  acids  as  carboxylic  acids  of  the  original 
hydrocarbons  in  question,  e.g.  phthalic  acid  is  benzene-dicar- 
boxylic  acid.  Many  names,  such  as  xylic  acid,  are  taken  from 
those  of  the  hydrocarbons  into  which  the  carboxyl  has  entered, 
while  others,  such  as  mesitylenic  acid,  indicate  the  hydro- 
carbons from  whose  oxidation  the  acids  result.  An  important 
principle  as  regards  nomenclature  depends  upon  the  fact  that 
aromatic  acids  can  be  derived  from  almost  every  fatty  acid  of 
any  consequence  by  the  exchange  of  H  for  CgH^,  e.g.  : 

CH3-CO2H,  acetic  acid ;  C^H^-CHo-COgH,  phenyl-acetic  acid. 

There  thus  exist  phenylated  acids  analogous  to  the  acids 
of  the  acetic,  glycollic,  succinic,  malic  and  tartaric  series,  etc. 

Atropic  acid,  C^Hr, — ^^qo.JI'  example,  may  be  designated 
a-phenyl-acrylic  acid,  and  so  on. 


404 


XXV.  AROMATIC  ACIDS. 


Properties,  Most  of  the  aromatic  acids  are  solid  crystalline 
substances,  generally  only  sparingly  soluble  in  water  and 
therefore  precipitable  by  acids  from  solutions  of  their  salts, 
but  often  readily  soluble  in  alcohol  and  ether.  The  simpler 
among  them  can  be  distilled  or  sublimed  without  decomposi- 
tion, while  the  more  complicated,  especially  phenolic  and 
poly-carboxylic  acids,  give  up  carbon  dioxide  when  heated; 
e.g.  salicylic  acid,  CgH4(OH).C02H,  breaks  up  thus  into  phenol 
and  COg.  Such  a  separation  of  carbonic  anhydride  is  effected 
in  the  case  of  those  acids  which  are  volatile  without  decom- 
position by  heating  e.g.  with  soda-lime;  in  polybasic  acids  the 
carboxyls  may  be  split  up  in  succession  : 

CeH,(C02H)2  =  CeH.CCO^H)  +  CO^  =  CeH^  +  2G0^. 

Occurrence.  A  large  number  of  the  aromatic  acids  are  found 
in  nature,  e.g.  in  many  resins  and  balsams,  and  also  in  the 
animal  organism  in  the  form  of  nitrogenous  derivatives  such 
as  hippuric  acid. 

Modes  of  formation, 

A.  Of  the  saturated  acids. 

1.  By  the  oxidation  of  the  corresponding  primary  alcohols 
or  aldehydes ;  e.g.  benzoic  acid  from  benzyl  alcohol. 

2.  By  the  oxidation  of  the  benzene  homologues  and  of  all 
the  compounds  which  are  derived  from  these  by  substitutions 
in  the  side  chain;  also  of  all  the  derivatives  of  those  com- 
pounds which  contain  halogen,  nitro-,  sulpho-,  etc.  groups, 
liydroxyl  or  carboxyl  in  place  of  benzene  hydrogen ; 

C6H5(CH3)  yields  CfiHglCO^H) 

cSicSkHj  " 

C6H3(CH3),(C2H5)  „  CeH3(CO,H)3 

CeHs-CH^tNH,,)  „  CeHs-CO^H 

CeH^CUCH,)  „  C6H4C1(C02H) 

C6H4(N02)(C2H5)  „  CeH^lNO^XCO^H) 

CeHjlOHj^lCHg)  „  CeHsCOHj^fCO^H) 

CeH4(CH3)(CO,H)  „  C,H4(CO,H)2 

C6H5-CH=CH-C02H     „  CeHj-CO^H. 

Should  there  be  several  side  chains  in  the  molecule,  they  are  usually 
all  converted  directly  into  carboxyl  by  chromic  acid,  whereas  by 


GENERAL  MODES  OF  FORMATION. 


405 


using  dilute  nitric  acid,  this  transformation  can  be  effected  step  by 
step,  e.g.  : 

C6H4(CH3)2  yield  first  C6H4(CH3)(C02H)  and  then  C6H4(C02H)2 
The  xylenes  Toluic  acids  Phthalic  acids. 

Nevertheless  the  three  classes  of  isomeric  benzene  derivatives  with 
two  side  chains  comport  themselves  differently.  The  para-compounds 
are  the  most  readily  oxidized  to  acids  by  chromic  acid  mixture  and 
then  the  meta-,  whereas  the  ortho-compounds  are  either  completely 
destroyed  by  it  (p.  326)  or  not  attacked  at  all.  The  last-named  may 
however  be  oxidized  in  the  normal  manner  by  nitric  acid  or  perman- 
ganate of  potash.  The  entrance  of  a  negative  group  (and  also  of 
hydroxyl)  renders  more  difficult  the  oxidation  of  an  alkyl-group  having 
the  o-position  with  regard  to  it  (cf.  p.  387). 

3.  By  the  saponification  of  the  corresponding  nitriles  (p. 
402). 

CgHg.CN  +  2H2O  =  CgHg.COgH  +  NH3. 

These  Nitriles,  which  can  be  prepared  from  the  ammonium 
salts  of  the  acids  in  the  same  manner  as  those  of  the  fatty- 
series,  result  from  the  following  syntheses  : 

(a)  By  distilling  the  potash  salts  of  the  sulphonic  acids  with 
potassium  cyanide  or  ferrocyanide  (Merz),  just  as  the  nitriles 
of  the  fatty  acids  are  formed  from  the  alkyl  sulphates  (p.  107): 

CgHg.SOgK  +  KCN  =  CgHg.CN  +  SO,K^. 

Nitriles  cannot  as  a  rule  be  prepared  from  chloro-benzenes, 
etc.  and  KCN,  (cf  p.  333) ;  the  halogen  is  more  readily 
replaced  by  cyanogen  if  sulpho-groups  are  likewise  present. 
Or  nitro-groups  (in  presence  of  halogens)  can  also  be  replaced, 
as  in  the  case  of  the  bromo-nitro-benzenes,  (B.  8,  1418). 

Benzyl  chloride,  CgH^ — CHgCl,  and  all  the  haloid  hydro- 
carbons which  are  substituted  in  the  side  chain,  on  the  other 
hand,  show  the  normal  ready  exchangeability  of  halogen  for 
cyanogen : 

CgH^— CH2CI  +  KCN  =  KCl  +  C.H^— CH2.CN 

Benzyl  cyanide. 

(b)  By  heating  the  mustard  oils  with  copper  or  zinc  dust  (  Weith) : 

CeHg.NCS  -f  2Cu  =  CgHgCN  -f  Cu^S. 

(c)  By  the  molecular  transformation  of  the  isomeric  iso-nitriles  at  a 


406 


XXV.  AROMATIC  ACIDS. 


somewhat  high  temperature :  (QjHg.NC  =  CdHg.CN).  The  nitriles 
may  be  prepared  indirectly  from  the  amines  by  botli  the  last  methods, 
and  also  by  exchanging  the  diazo-group  for  the  cyanogen  one  (p.  363). 

{d)  By  eliminating  the  elements  of  water  from  the  oximes  of  the 
aldehydes  (p.  134)  by  means  of  acetyl  chloride  : 

C6H5.CH=]Sr.OH  =  CfiHg.CN  +  HgO. 

Benzaldoxime. 

4.  Syntheses  effected  by  the  action  of  carbonic  acid  or  its 
derivatives : 

(a)  Benzoic  acid,  etc.  is  produced  by  the  action  of  carbon 
dioxide  upon  mono-bromo-benzene,  etc.  in  presence  of  sodium, 
{KekuU) : 

C^H.Br  +  CO2  +  2Na  =  C^H^.COgNa  +  NaBr. 

{h)  By  the  action  of  phosgene,  COClg,  or  also  of  COg,  upon 
benzene  and  its  homologues  in  presence  of  AlgClg  (Friedel 
and  Crafts) : 

CgHg  +  COCI2  =  CgH^.COCl  +  HCl. 

Acid  chlorides  are  first  formed  here,  which  are  then  to  be  decomposed 
by  water.  By  the  further  action  of  these  chlorides  upon  benzene  in 
presence  of  AlgClg,  ketones  result  (see  benzophenone. ) 

COCI2  acts  with  particular  ease  upon  tertiary  amines  : 

C6H5.N(CH3)2  +  COCI2  =  C6H4[N(CH3)2].C0C1  +  HCl. 
(c)  By  the  action  of  carbamic  chloride,  CI — CO.NHg,  upon  benzene 
in  presence  of  AlgClg,  there  result  in  an  analogous  manner  the  amides 
of  the  aromatic  acids,  (Gatterman  and  Schmidt,  B.  20,  862) : 

CgH^CCHs)  +  CI-CO.NH2  =  CeH4{™3^jj^  +  HCl. 

{d)  By  the  action  of  sodium  upon  a  mixture  of  brominated 
benzenes  and  chloro-carbonic  ether  (Wurtz);  in  this  case  the 
compound  ethers  are  first  formed,  but  these  are  easy  to 
saponify : 

CgH^Br  +  C1.C02(C2H5)  +  2Na 

=  C6H5.C02(C,H5)  +  NaBr  +  NaCl. 

(e)  The  phenolic  acids  are  produced  by  passing  carbon 
dioxide  over  heated  sodium  phenate,  (Kolbe;  see  p.  419) : 

CeHg.ONa  +  COg  =  C6H4(OH).C02Na. 


GENERAL  MODES  OF  FORMATION. 


407 


In  the  case  of  the  phenols  of  higher  atomicity,  e.g.  resorcin,  it  often 
suffices  merely  to  heat  with  a  solution  of  ammonium  carbonate  or 
potassium  bicarbonate,  (B.  13,  930).  Chlorocarbonic  ether  acts  in  a 
similar  way. 

(/)  i?-Oxy-acids  are  formed  by  the  action  of  carbon  tetra- 
chloride upon  phenols  in  alkaline  solution,  (B.  10,  2185) : 
CeH.ONa  +  CCI4  =  C6H,(OH).CCl3  +  NaCl. 

C6H4(OH).CCl3  +  4NaOH  =  CeH4(OH).C02Na  +  3NaCl  +  2H2O. 

When  chloroform  is  employed,  the  aldehydes  of  these  (0- 
and  p')  oxy-acids  result  in  an  analogous  manner : 

CeHg.OH  +  CHCI3  +  3NaOH 

=  C6H4.(OH)CHO  +  3NaCl  +  2H2O. 

Methylene  chloride,  CHgClg,  also  shows  a  similar  behaviour,  with 
the  formation  of  aromatic  oxy-alcohols. 

{g)  By  heating  the  sulphonates  with  sodium  formate  ( F.  Meyer) : 

CeHg.SOsK  +  HCO2K  =  C6H5.CO2K  +  HSO3K. 
5.  Aceto-acetic  ether  and  malonic  ether  syntheses,  etc. 

{a)  For  the  formation  of  phloroglucin-tricarboxylic  ether  from  sodio- 
malonic  ether,  see  p.  321. 

(b)  Sodio-aceto-acetic  ether  yields  a  complicated  benzene  derivative 
in  an  analogous  manner,  (B.  18,  3460). 

(c)  For  the  production  of  hydroquinone-dicarboxylic  ether,  etc.  from 
ethyl  succinate  or  from  brom-aceto-acetic  ether,  see  p.  321. 

(d)  For  the  action  of  aceto-acetic  ether  upon  phenols,  see  p.  408. 

(e)  Aceto-acetic  ether  acts  upon  the  haloid  derivatives  which 
are  substituted  in  the  side  chain,  e.g.  benzyl  chloride,  exactly  as 
in  the  fatty  series,  with  the  formation  of  the  more  complicated 
ketonic  acids,  which  again  are  capable  of  undergoing  either 
the  "  acid  decomposition "  or  the  "  ketone  decomposition " 
(p.  225),  e.g.  : 

CgH^— CH2CI  +  CH3— CO— CHNa— CO2R 

=  CH3— CO— CH(C7H7)-C02R  +  NaCl. 
^  ,  ' 

Benzyl-aceto-acetic  ether. 

CH3— CO— CH(C7H^)— CO2R  +  H2O 

=  CgHs— CH^— CHg-  CO,R  +  CH3.CO2H. 

Phenyl-propionic  ether. 


408 


XXV.  AROMATIC  ACIDS. 


6.  Alcohol -acids  and  ketone-acids  are  formed  by  exactly  the  same 
methods  as  in  the  fatty  series  (p.  207),  e.g.  mandelic  acid  by  the  com- 
bination of  hydrocyanic  acid  with  benzaldehyde,  and  saponification  of 
the  resulting  nitrile,  (B.  14,  239,  1965) : 

CgHg— CHO  +  HCN  =  CgHs-CHlOH)— CN; 

or,  from  a-chlorophenyl-acetic  acid,  (B.  14,  239)  : 

CeHg-CHCl-COgH  +  KOH  =  C6H5-CH(OH)-C02H  +  KCl. 

7.  Hydro-^-cumai'ic  acid,  hydrocinnamic  acid,  ^-oxyphenyl- 
acetic  acid,  etc.  are  produced  by  the  decay  of  albumen,  (B. 
16,  2313). 

B.  Of  the  unsaturated  acids. 

1.  From  the  mono-haloid  substitution  products  of  the 
saturated  acids  in  the  normal  manner  (p.  164);  similarly 
from  the  corresponding  nitriles,  primary  alcohols,  etc.,  as 
in  the  case  of  the  saturated  compounds. 

2.  According  to  the  so-called  Ferkin  reaction,  by  the  action 
of  aromatic  aldehydes  upon  fatty  acids.  Thus,  when  benzalde- 
hyde is  heated  with  acetic  anhydride  and  sodium  acetate, 
cinnamic  acid  is  formed  : 

CeH5.CHO  +  CH3.C02Na  =  CgH^— CH=CH— C02Na  +  HgO. 

The  acetic  anhydride  only  acts  as  a  dehydrating  agent  in 
this  instance,  the  reaction  taking  place  between  the  sodium 
acetate  and  the  aldehyde,  (cf.  A.  216,  9). 

Oxy-acids  are  formed  as  intermediate  products  here  by  a  reaction 
similar  to  "aldol  condensation"  (p.  134);  in  the  above  case,  for 
instance,  /3 -phenyl -hydracry lie  acid,  CgHg— CH(OH)— CHg— COgH. 

This  reaction  also  takes  place  with  the  oxy- aldehydes,  with  the 
homologues  of  acetic  acid,  and  also  with  dibasic  acids,  e.g.  malonic. 

3.  Cinnamic  acid  results  in  an  analogous  manner  by  the  action  of 
benzal  cloride  upon  sodium  acetate  (Caro)  : 

CeHs-CHClg  +  CHg— CO2H  =  CgHg— CH=CH— COgH  +  2HC1. 

4.  By  the  action  of  aceto-acetic  ether  upon  the  phenols  in  presence 
of  concentrated  H2SO4,  there  are  formed  unsaturated  phenolic  acids  or 
their  anhydrides  (B.  16,  2119 ;  17,  2191),  e.g.: 

WOH)  H-  (0H).C(CH3)=CH   ^  C(CH3)=CH  ^ 

^                          HO~CO               ^0  —CO 
^  ^  ^   

Aceto-acetic  ether.  Methyl-cumarin. 


MONOBASIC  AROMATIC  ACIDS. 


409 


4a.  Malic  acid  acts  upon  phenols  in  presence  of  H2SO4  in  an 
analogous  manner,  reacting  here  probably  as  the  half-aldehyde  of 
malonic  acid,  CHO-CH2— CO2H  (  =  malic  acid,  C2H3(OH)(C02H)2, 
-CO2H2  [see  p.  222]),  {v,  Pechmann,  B.  17,  929)  : 

PH  OH  +  0=CH-CH2  _  /CH^CH 


Malonic  aldehyde-acid.  Cumarin. 


A.  Monobasic  Aromatic  Acids. 

(See  table,  p.  410.) 

Constitution  and  Isomers.  The  cases  of  isomerism  in  the 
aromatic  acids  are  easy  to  tabulate.  An  isomer  of  benzoic 
acid  is  neither  theoretically  possible  nor  actually  known. 
Carboxylic  acids  of  the  formula  CgHgOg  may  however  be 
derived  from  toluene  by  the  entrance  of  carboxyl  either  into 
the  benzene  nucleus  or  into  the  side  chain,  thus  : 

C6H,(CH3)(C02H)  CeH5.CH2.CO2H 

(3)  Toluic  acids.  Phenyl-acetic  acid. 

The  behaviour  of  these  acids  upon  oxidation  yields  proof  of 
their  constitution,  the  former  going  into  the  phthalic  acids 
and  the  latter  into  benzoic. 

Of  acids  CgH^oOg,  a  large  number  of  isomers  are  already 

known  (see  table).    Hydrocinnamic  acid  and  hydratropic  acid 

are  phenyl-propionic  acids,  the  former  /5-  and  the  latter  a-, 

corresponding  to  the  lactic  acids ;  the  isomeric  relations  of  the 

fatty  acids  thus  repeat  themselves  here  also.    The  a-xylic  acids, 

CH  C  H 

Q^l^^<^^Yi  CO2H'  ethyl-benzoic  acids,  ^Q^4<iQQ  fj? 

stand  in  the  same  relation  to  each  other  as  aceto-acetic  acid, 
CH3 — CO — CH2 — COgH,  does  to  propionyl-formic  acid, 
CgH^— CO— COgH,  and  they  all  yield  phthalic  acids  upon 
oxidation.  Lastly,  mesitylenic  acid  and  its  isomers  are 
dimetliyl-benzoic  acids,  and  are  oxidizable  to  benzene-tri- 
carboxylic  acids. 

[Continued  on  412. 


1 


410  XXV.  AROMATIC  ACIDS. 


Summary  of  the  Monobasic 


1.  Monatomic  saturated  Acids. 

M.Pt. 

00 

Q 

o 

o 

0-,  m-,  p-Toluic  acids,  .... 
rHydrocinnamic  acid,  .... 

Ethyl-benzoic  acid,  .... 

Mesitylenic  acid,    .     (1:3: 5)^ 
Xylicacid,     .    .    .  (1:2:4)1 
^Paraxylic  acid,  .    .     (1:3:4) J 

jCumic  acid,   .    .    .   (1  :4,  iso-) 
etc. 

CaH^-CH^-CO^H 

^6    — CJHg — CH2 — CO2H 

P  XT  ^CHg 

^6"4\pTT       PO  TT 
^6"4<.C02H  \p- 

n  TT  ^(0113)2  * 
D  TT  ^^3^7 

^6tl4<\C02H 

120° 

76° 

102° 
110° 
180° 

47° 
liq. 

42° 

62° 
110° 

166° 

126° 

163° 

116° 

2.  Monatomic  unsaturated  Acids. 

O 

00 

o 

C9 

rCinnamic  acid,  

{Phenyl-propiolic  acid,     .    ,  . 

CgHg— CH=CH— CO2H 
CfiHg— CEEC-CO2H 

133° 
106° 
136^ 

6.  Unsaturated  Phenolic  Acids. 

0 

00 

W 

j  Cumaric  acid  (0-,  p-),  .... 
etc. 

C6H4(OH)- CH=CH-C02Hg; 

207° 
206° 

*  1  : 3  :  5,  etc. ;  COgH  in  position  1. 


SUMMARY. 


411 


Aromatic  Acids. 


3.  Diatomic  saturated  Phenolic  Acids. 


d  r  Salicylic  acid  (1:2)  | 

[m-,  p-Oxybenzoic  acids  J 
[Anisic  acid  (1:4),  

Cs  {Oxy-toluic  acids,  

etc. 

IHydro-para-cumaric  acid  (1  : 4), 
^Tyrosine  (1:4),  

etc. 


C6H4(O.CH3).C02H] 

C6H3(CH3)<^QQ  Tj 


-CH,-COoH 


4.  Diatomic  saturated  Alcohol-  and  Ketone- Acids. 


C6H5-CH(OH)-C02H 

183° 

C9 

117" 

Cs 

1  Benzoyl-f ormic  acid,  .... 

CeHg— CO-CO2H 

65° 

C9 

|Benzoyl-acetic  acid,  .... 

CeHg— CO— CH2— CO2H 

liq. 

5.  Tri-  and  polyatomic  Phenolic  Acids. 


C7  { Protocatechuic  acid  (1:3:4) 

[Vanillic  acid,  

Cg  -[Orsellinic  acid,  

I Gallic  acid,  
[Tannin,  
Quinic  acid,  

etc. 


CaH3(OH)2(C02H) 
CeH5(OH)(O.CH3)(C02H)] 
CeH^lCH^liOHMCOsH) 
QH,(OH)3(C02H) 

CoH.(He)(OH)4(CO,H) 


412 


XXV.  AROMATIC  ACIDS. 


As  is  easily  seen,  the  followiDg  acids  are  isomeric  with  cumic  acid 
(p-isopropyl-benzoic  acid),  CioHigOg:  first,  ^-normal-propyl-benzoic  acid 
and  the  corresponding  o-  and  m-compounds,  then  the  methyl-ethyl- 
benzoic  acids,  trimethyl-benzoic  acids,  phenyl-butyric  acids,  and  so 
on. 

As  instances  of  isomers  among  the  unsaturated  acids  we  may  take 
cinnamic  and  atropic  acids  (analogous  to  jS-  and  a-chlor-acrylic  acids, 
p.  169). 

Further,  the  oxy-toluic  acids,  C6H3(Crr3)(OH)(C02H),  are  isoirieric 
with  mandelic  acid,  CeHg — CH(OH) — CO2H,  the  former  being  oxidizable 
to  oxy-phthalic  acids,  C6H3(OH)(C02H)2,  and  the  latter  to  benzoic  acid; 
the  hydrocumaric  acids,  C9H10O3,  are  likewise  isomeric  with  tropic 
acid.  The  first-named  go  into  oxy-benzoic  acids  upon  oxidation  and 
the  last  into  benzoic. 


1.  Monatomic  Saturated  Acids. 

Benzoic  Acid. 

Benzoic  acid,  CgH^.COgH,  was  discovered  in  gum  benzoin 
in  1608  and  prepared  from  urine  by  Scheele  in  1785.  Its 
composition  was  established  by  Liebig  and  Wohler^s  classical 
researches  in  1832.  It  occurs  in  nature  in  gum  benzoin,  from 
which  it  may  be  obtained  by  sublimation  ("  Acidum  benzoicum 
ex  resina  ") also  in  dragon's  blood  (a  resin),  in  Peru  and  Tolu 
balsams,  in  castoreum  and  in  cranberries.  It  is  present  in  the 
urine  of  horses  in  combination  with  glycocoU  as  hippuric  acid, 
from  which  it  results  upon  boiling  with,  hydrochloric  acid 
('^acidum  benzoicum  ex  urina").  It  is  obtained  on  the  large 
scale  ("ac.  benz.  e  toluole")  as  a  bye-product  in  the  manufac- 
ture of  oil  of  bitter  almonds  from  benzyl  chloride  or  benzal 
chloride.  The  acid  may  also  be  got  by  heating  benzo-tri- 
chloride  with  water  to  a  somewhat  high  temperature : 

CgH^.CClg  +  2H2O  =  C6H,.C02H  +  3HCI. 

Benzoic  acid  is  also  present  in  coal  tar.  It  crystallizes  in 
colourless  glancing  plates  or  flat  needles,  sublimes  readily  and 
is  volatile  with  steam,  its  vapour  having  a  peculiar  irritating 
odour  and  giving  rise  to  coughing.  M.  Pt.  121°,  B.  Pt.  250°. 
It  is  readily  soluble  in  hot  water  but  only  slightly  in  cold. 


BENZOIC  ACID. 


413 


When  heated  with  lime,  it  is  decomposed  into  benzene  and 
carbon  dioxide.  It  is  used  in  medicine  and  in  the  manufac- 
ture of  aniline  blue.  Some  of  its  salts  crystallize  beautifully, 
e.g,  calcium  benzoate,  (CgH5.C02)2Ca  +  SHgO,  in  glancing 
prisms  or  needles. 

Ethers^  Anhydrides^  Amides,  etc,  of  Benzoic  Acid, 

The  ethers,  e.g.  Methyl  benzoate,  C6H5.C02(CH3),  B.  Pt. 
190°,  and  Ethyl  benzoate,  GoR^.GO^iC^'il^),  B.  Pt.  211°,  are 
prepared  as  given  on  p.  174  (by  means  of  HCl),  and  are 
liquids  of  pleasant  aromatic  odour  which  boil  for  the  most 
part  without  decomposition. 

Benzyl  benzoate,  CgH5.C02.(CH2.CgH5),  is  present  in  the 
balsams  of  Peru  and  Tolu  (from  Myroxylon). 

Benzoyl  chloride,  CgHg.CO.Cl  {Liehig  and  Wohler),  which 
can  be  obtained  by  acting  upon  the  acid  with  PCl^,  is  the 
complete  analogue  of  acetyl  chloride  but  more  stable  than 
the  latter,  since  it  is  only  slowly  saponified  by  cold  water, 
although  quickly  by  hot. 

Benzoyl  cyanide,  CeHg.CO.CN  [from  benzoyl  chloride  and  Hg(CN)2], 
serves  for  the  synthesis  of  benzoyl-formic  acid  (p.  424). 

Benzoic  anhydride,  (CgH^. 00)20  (Gerhardt),  is  exactly 
analogous  to  acetic  anhydride.  It  crystallizes  in  prisms 
insoluble  in  water,  boils  without  decomposition  and  becomes 
hydrated  on  boiling  with  water. 

Benzamide,  CgH5.CO.NH2,  exactly  corresponds  with  acet- 
amide  and  is  easily  prepared  from  benzoyl  chloride  and 
ammonia  or  ammonium  carbonate.  It  forms  glancing  mother- 
of-pearl  plates  of  130°  M.  Pt.,  boils  without  decomposition  and 
is  readily  soluble  in  hot  water. 

The  amido -hydrogen  of  benzamide  may  be  substituted  by  alcohol 
radicles  such  as  phenyl,  etc.  with  the  formation  e.g.  of  Benzanilide, 
CgHg.CO.NHCgHg,  the  anilide  of  benzoic  acid,  a  compound  which  can 
be  readily  prepared  from  aniline  and  benzoic  acid.  It  crystallizes  in 
colourless  plates,  M.  Pt.  158°,  distils  unchanged,  and  is  in  fact  the 
complete  analogue  of  acetanilide. 


414 


XXV.  AROMATIC  ACIDS, 


Metallic  derivatives  of  benzamide  are  also  known,  e.g.  Benzamide- 
silver  (see  acetamide). 

Hippuric  acid,  benzamido-acetic  acid, 

C9H9NO3,  =  ^6^5^  is  an  amido-derivative 

of  benzoic  acid,  being  derived  from  the  latter  and  glycocoll 
(amido-acetic  acid) ;  it  may  be  prepared  e.g,  by  heating 
benzoic  anhydride  with  glycocoll,  (B.  17,  562).  Hippuric 
acid  is  present  in  the  urine  of  horses  and  of  other  herbivora. 
When  benzoic  acid  or  toluene  is  taken  internally,  it  is  voided 
in  the  form  of  hippuric  acid.  It  crystallizes  in  rhombic  prisms, 
sparingly  soluble  in  cold  water  but  readily  in  hot,  decomposes 
on  being  heated,  and  forms  salts,  ethers,  nitro-derivatives,  etc. 


Chloro-,  Nitro-  and  Sulph-amido-benzoic  Acids. 

The  hydrogen  of  benzoic  acid  is  replaceable  by  halogen  with  the 
formation  e.g.  of  Chloro-benzoic  acid,  C6H4CI.CO2H.  In  such  forma- 
tion of  mono-substitution  products  the  halogen  takes  up  the  meta- 
position  to  the  carboxyl.  Nitric  acid  (especially  a  mixture  of  nitric 
and  sulphuric  acids)  nitrates  readily,  m- Nitro -■benzoic  acid  being  chiefly 
produced,  together  with  a  smaller  quantity  of  the  ortho-  and  a  very 
little  of  the  para-acid. 

NTT 

The  Amido-benzoic  acids,  ^6^4:'^qqq}19  which  result  from 

the  reduction  of  the  nitro-acids  by  tin  and  hydrochloric  acid, 
etc.,  are  at  the  same  time  bases  and  acids,  and  therefore 
similar  to  glycocoll  in  chemical  character ;  they  combine  with 
hydrochloric  acid,  hydrochloric  acid  and  platinic  chloride,  etc., 
as  well  as  with  bases.  With  regard  to  their  constitution,  cf. 
p.  308. 

o-Amido-benzoic  acid  is  also  obtained  from  the  oxidation  of  indigo 
with  manganese  dioxide  and  caustic  soda,  and  is  often  termed 
Anthranilic  acid ;  it  forms  (in  contradistinction  to  the  m-  and  ^^-acids) 

CO 

an  intramolecular  anhydride,  Anthranil,  C6H4<^-^jj^. 

Diamido-benzoic  acids,  Cf;H3(NH2)2(C02H),  (see  p.  314).  The  Diazo- 
benzoic  nitrates,  C6H4<^q^^'~'^^^  possess  in  full  degree  the  charac- 


BENZO-NITRILE  ;  PHENYL- ACETIC  ACID. 


415 


tcristics  of  the  diazo-compounds  already  described,  and  show  the  same 
transformations  ;  they  yield  benzoic  acid  when  boiled  with  alcohol, 
oxy-benzoic  acid  with  water,  and  iodo-benzoic  acid  with  hydriodic  acid, 
etc. 

Diazo-amido-compounds  are  also  known. 

The  Sulpho-benzoic  acids,  C6H4(S03H)(COaH),  are  dibasic  acids. 
One  of  the  ammonia  derivatives  of  o-sulpho-benzoic  acid  is  that 

SO 

eminently  sweet  substance,  the  so-called  "Saccharine,"  C6H4<^'^q^^NH, 

i.e.  o-sulpho-benzoic  imide,  or  o-benzoyl  sulphone-imide,  an  amide  com- 
parable with  succinimide, 

Benzo-nitrile. 

Benzo-nitrile,  CgH^CN  (cf.  p.  405),  is  an  oil  which  smells 
like  oil  of  bitter  almonds  and  boils  at -191°.  It  is  prepared 
either  by  the  action  of  PCI5  upon  benzamide  (p.  183),  or  by 
distilling  benzoic  acid  with  ammonium  sulphocyanide.  It 
possesses  all  the  properties  of  a  nitrile,  combining  slowly  with 
nascent  hydrogen  to  benzylamine,  readily  with  halogen 
hydride  to  imido-chloride,  with  amines  to  amidines  (p.  185  ; 
cf.  A.  192,  1),  with  hydroxylamine  to  amidoximes  (p.  186), 
and  so  on. 

AcidSy  OgHgOg. 

1.  The  three  Toluic  acids,  CgH4(CIl3)(C02H),  can  be  pre- 
pared from  the  three  xylenes.    Isomeric  with  them  is  : 

2.  Phenyl-acetic  acid,  a-toluic  acid,  CgH5.CIl2.C02lI, 
(CannizarOy  1855).  This  acid  differs  characteristically  from  its 
isomers  by  its  behaviour  upon  oxidation  (see  p.  409).  It 
results  synthetically  from  benzyl  chloride  and  potassium 
cyanide,  Benzyl  cyanide,  C6lI5.CH2.CN  (B.  Pt.  229°),  being 
formed  as  intermediate  product ;  it  crystallizes  in  glancing 
plates,  M.  Pt.  76°,  B.  Pt.  262°. 

It  is  capable  of  undergoing  substitution  either  in  the  benzene 
nucleus  or  in  the  side  chain.  In  the  latter  case  there  are 
formed  compounds  such  as  : 


416 


XXV.  AROMATIC  ACIDS. 


Phenyl-chlor-acetic  acid,  C^jHr,— CHCl— CO^H,  and  : 
Phenyl-amido-acetic  acid,  CtjHg— CH(NH2)— COgH,  compouuds  which 
possess  precisely  the  same  character  as  monochlor-acetic  and  amido- 
acetic  acids.  Isomeric  with  phenyl-amido-acetic  acid  are  the  three 
Amido-phenyl-acetic  acids,  C(jH4(NH.)— CHg— CO.^H,  of  which  the 
o-acid  is  interesting  on  account  of  its  close  relation  to  the  indigo  group. 
It  does  not  exist  in  the  free  state  but  goes  into  an  intramolecular 
anhydride,  oxindole  (p.  434),  when  set  free,  thus  : 

^6H4<cH2-CO,H  =  C6H4<^^^>CO  +  H2O. 

Such  a  formation  of  intramolecular  anhydride  is  of  very  frequent 
occurrence  in  ortho-compounds  of  this  kind,  in  contradistinction  to  the 
m-  and  2>compounds  (see  Indole).  Theoretically  it  may  take  place  in 
the  above  instance  in  two  difierent  ways,  viz.,  either  by  the  elimination 
of  a  hydrogen  atom  of  the  amidogen  together  with  OH,  or  of  both  of 
the  amidogen  H-atoms  with  0.  These  two  cases  are  distinguished  by 
Baeyer  3i&  "  Lactame  formation  "  and  *' Lactime  formation," 

Oxindole  is  a  lactame,  while  isatin,  CgH4<^^Q^C.0H  (p.  433),  is  a 
lactime  of  o-amido-phenyl-glyoxylic  acid  (p.  424). 

Both  lactames  and  lactimes  contain  hydrogen  which  is  readilj 
replaceable  ;  in  the  former  case  it  is  present  in  the  amido-group  and  in 
the  latter  in  the  hydroxyl. 

If  the  compounds  which  result  from  the  replacement  of  hydrogen  by 
alkyl  are  very  stable,  the  alkyl  in  them  is  linked  to  the  nitrogen  and 
they  are  derivatives  of  the  lactames  ;  if  on  the  contrary  they  are  easily 
saponifiable,  the  alkyl  is  linked  to  oxygen  and  they  are  ethers  of  the 
lactimes. 


Acids,  CgHjoOg. 

1.  Dimethyl-benzoic  acids,  xylene-carhoxylic  acids, 
CgH3(CH3)2(C02H).    Of  these  six  are  possible  and  four  are 
known. 

Mesitylenic  acid,  (COgH  :  CH3 :  CH3  =  1:3:5),  results  from  the 
oxidation  of  mesitylene,  and  the  two  isomeric  Xylic  acids  (1  :  2  :  4)  and 
Paraxylic  acid  (1:3:4,  see  table,  p.  410)  from  that  of  pseudo-cumene. 
Isomeric  with  them  are  : 

2.  a-Xylic  acid,  GQ^^[Qn^)—{CIL^—QO^B.)  (1:4),  and  the  Ethyi 
benzoic  acids,  C6H4(C2H5)C02H,  both  of  which  are  bi-derivatives  of 
benzene,  (cf.  p.  409  and  also  the  table). 


HYDROCINNAMIC  ACID;  CINNAMIC  ACID.  417 


3.  The  Phenyl-propionic  acids,  C^jH^— C2H4-  -CO^H.  These 
may  be  either  a-  or  ^-derivatives  of  propionic  acid. 

^-Phenyl-propionic  acid  or  Hydrocinnamic  acid, 
CgH^ — CH2 — CH2 — CO2H,  results  from  the  action  of  sodium 
amalgam  upon  cinnamic  acid  and  from  the  decay  of  albuminous 
matter.    Fine  needles ;  M.  Pt.  47°,  B.  Pt.  280^ 

Many  substitution  products  etc.  of  this  acid  are  known,  among 
which  may  be  mentioned  o-Nitro-cinnamic  dibromide, 

C6H4<^^g^^_^jj-g^_QQ  jj,  a  compound  nearly  related  to  indigo 

(p.  431);  further,  Phenyl-a-amido-propionic  acid  (phenyl-alanine), 
CeHg— CHg— CHtNHg)— COgH,  and  Phenyl-jS-amido-propionic  acid, 
CgHg — CH(NH2) — CH2 — CO2H,  both  of  which  can  be  prepared  syntheti- 
cally, the  former  being  likewise  produced  by  the  decay  of  albumen  and 
by  the  germination  of  {e.g.)  Lupinus  luteus. 

NH 

The  isomeric  o-Amido-liydrocinnamic  acid,  C6H4<^^     —CO  H 

not  stable,  but  goes  immediately  into  its  lactame,  hydro-carbostyril, 
C9H9ON,  a  quinoline  derivative. 

Hydratropic  acid,  CgHg — CH(CH3)— CO2H,  is  obtained — as  its  name 
implies — by  the  addition  of  hydrogen  to  atropic  acid.  It  is  liquid  and 
volatile  with  steam. 

Acids,  C1QH12O2. 

Among  these  may  be  mentioned  Cumic  acid  or  p-isopropyl- 
benzoic  acid,  CgH4(C3H.jr)(C02H),  which  is  obtained  by  oxidizing 
Roman  oil  of  cumin  with  permanganate  of  potash;  (this  oil 
contains — in  addition  to  cymene — its  aldehyde,  cumic  alde- 
hyde). It  also  results  from  the  oxidation  of  cymene  in  the 
animal  organism,  the  propyl  group  being  here  changed  into 
the  isopropyl  one.  It  crystallizes  in  plates,  boils  without 
decomposition,  and  yields  cumene  when  distilled  with  lime. 

The  isomeric  normal  Propyl-benzoic  acid  has  also  been  prepared  (see 
p.  330). 


2.  Monatomic  unsaturated  acids. 


1.  Cinnamic  acid,  GgEfi^,  =  CgH^— CH-.CH-CO2H, 

( 506 )  2  D  " 


418 


XXV.  AROMATIC  ACIDS. 


{Trommsdorfy  1780),  occurs  in  Peru  and  Tolu  balsams  and  also 
in  storax,  and  may  be  prepared  as  given  at  p.  408.  It  crystal- 
lizes in  needles  or  prisms,  readily  soluble  in  hot  water ;  M.  Pt. 
133°,  B.  Pt.  290°.  When  fused  with  potash,  it  is  split  up  into 
benzoic  and  acetic  acids,  going  into  the  former  also  upon 
oxidation.  It  yields  salts,  compound  ethers,  etc. ;  also  HC1-, 
HBr-,  HI-,  ClOH-,  \jv^-  etc.  addition  compounds,  e.g.  cinnamic 
dibromide  (phenyl-dibromo-propionic  acid),  CgH^ — CHBr — 
CHBr — CO2H.  Further,  the  hydrogen  in  the  benzene  nucleus 
may  be  replaced  by  CI,  Br,  NOg,  NHg,  etc.;  thus,  upon  nitrat- 
ing cinnamic  acid  we  obtain  : 

0-  and  ^-Nitro-cinnamic  acids,  ^6H4<CcH— CH  CO  H 

the  first  of  which  is  of  importance  on  account  of  its  relation  to 
indigo.     On  reduction  it  yields  (?-Ainido-cinnamic  acid, 
NH 

CgH4<^Qjj^Qjj  QQ  jj  (fine  yellow  needles),  which  readily 

gives  up  water  and  goes  into  its  lactime  carbostyril  (a-oxy- 

.  .  ^_  .CH=C(OH) 
qumohne),  G^^<^  N=CH  ' 

Diazo-cinnamic  acids  are  also  known. 

The  cinnamic  acids  which  are  chlorinated  in  the  side  chain  show 
interesting  isomeric  relations,  (B,  15,  16 ;  19,  1380). 

The  radicle  of  cinnamic  acid,  ^,e.  (CgHg — CH=OH — CO),  is  termed 
*'cinnamyl,"  and  the  group  (CeHg — CH=CH),  cinnamenyl." 

2.  Atropic  acid,  CgHgOg,  is  a  decomposition  product  of  atropine.  It 
crystallizes  in  monoclinic  tables  and  can  be  distilled  with  steam.  It 
breaks  up  into  formic  and  a-toluic  acids  when  fused  with  potash,  this 
decomposition  taking  place  at  the  point  of  the  double  bond,  as  in  the 
cases  of  cinnamic  acid  and  the  unsaturated  acids  of  the  fatty  series. 

3.  (7)-Plienyl-isocrotonic  acid,  CgHg — CH=CH — CHg — COgH,  results 
upon  heating  benzaldehyde  with  sodium  succinate  and  acetic  anhydride, 
(  W.  H.  Ferkin,  sen. ) : 

CHo— CO2H  ^C— CO2H 

CHo— CO2H  CHo— COoH 


Phenyl-paraconic  acid. 


,^CH 

=  CgH^-CH    I  +  CO,. 

CH,— COoH 


PHENYL-PROPIOLIC  ACID ;  PHENOLIC  ACIDS.  419 


It  is  of  interest  on  account  of  its  conversion  into  a-naphthol  upon 
boiling  (see  p.  466). 

4.  Phenyl-propiolic  acid,  CgHgOg,  =  CgH^— C=C— COgH 
(Glaser,  1870),  is  formed  by  the  addition  of  bromine  to  ethyl 
cinnamate  and  subsequent  heating  of  the  dibromide, 
C^Hg— CHBr=CHBr— CO2C2H5,  so  obtained  with  alcoholic 
potash  (just  as  ethylene  is  converted  by  bromine  into 
ethylene  bromide,  and  the  latter  decomposed  into  acetylene 
by  potash).  It  crystallizes  in  long  glancing  needles  which  can 
be  sublimed;  M.  Pt.  136-137'.  When  heated  with  water 
to  120°,  it  breaks  up  into  COg  and  phenyl-acetylene  (p.  332). 
It  can  be  reduced  to  hydrocinnamic  acid  and  transformed  into 
benzoyl-acetic  acid. 

^?-Nitro-phenyl-propiolic  acidjCgH^-cC^Q^Q  CO  H 

is  prepared  in  a  manner  analogous  to  that  just  given,  viz.,  by 
the  addition  of  Brg  to  ethyl  (?-nitro-cinnamate  and  treatment  of 
the  resulting  bromide  with  alcoholic  potash,  (A.  212,  240).  It  is 
employed  technically  on  account  of  its  relation  to  indigo  (see 
p.  431).  It  breaks  up  into  COg  and  o-nitro-phenyl-acetylene 
upon  boiling. 


3.  Diatomic  (saturated)  Phenolic  Acids. 

For  modes  of  formation,  see  p.  406.  These  acids  may  also  be 
obtained  by  the  oxidation  of  the  homologues  of  phenol  and  of 
the  oxy-aldehydes,  which  is  effected,  among  other  methods, 
by  fusing  with  alkalies. 

The  phenolic  acids  form  salts  both  as  carboxylic  acids  and 
as  phenols,  salicylic  acid,  for  instance,  the  two  following  . 
classes : 

**  Neutral "   and    "  Basic  "  sodium  salicylate. 

The  first  of  these  two  salts  is  not  decomposed  by  COg,  while 
the  second,  as  the  salt  of  a  phenol,  is  decomposed  by  it  and 


420 


XXV.  AROMATIC  ACIDS. 


converted  into  the  first.  The  diatomic  phenolic  acids  behave 
therefore  like  monobasic  acids  towards  sodium  carbonate. 
When  both  of  the  hydrogen  atoms  are  replaced  by  alkyl,  there 
are  formed  compounds  such  as  C(5H4(OC2H5).C02(C2H5),  which 
are  only  half  saponified  upon  being  boiled  with  potash  [e.g, 
to  C(5H4(OC2H5).C02H].  Such  ether-acids  possess  completely 
the  character  of  monobasic  acids,  their  alcoholic  radicle  being 
only  eliminated  by  hydriodic  acid  at  a  rather  high  temperature. 
(Cf.  p.  382.) 

The  o-oxy-acids  (COgH  :  0H=1  :  2)  are,  in  contradistinction  to  their 
isomers,  volatile  with  steam,  give  a  violet  or  blue  colouration  with  ferric 
chloride,  and  are  readily  soluble  in  cold  chloroform. 

The  771-oxy-acids  are  more  stable  than  the  o-  and  ^-compounds ; 
while  most  of  the  latter  break  up  into  carbon  dioxide  and  phenols  when 
quickly  heated  or  when  acted  on  by  hydrochloric  acid  at  120°,  the 
former  remain  unaltered. 

The  phenolic  acids  are  much  more  easily  convertible  into 
substitution  products,  etc.  by  halogens  or  nitric  acid  than  the 
monatomic  monobasic  acids,  just  as  the  phenols  are  far  more 
readily  attacked  than  the  benzene  hydrocarbons. 


Oxy-henzoic  acids,  C6H4(OH)C02H. 

Salicylic  acid,  o-oxybenzoic  acid,  (COgH  :  OH  =  1:2). 

This  acid  was  discovered  by  Firia  in  1839. 

Occurrence,  In  the  blossom  of  Spiraea  Ulmaria,  as  methyl 
ether  in  oil  of  winter  green,  etc. 

Formation.  By  the  oxidation  of  saligenin ;  by  fusing 
cumarin,  indigo,  o-cresol,  etc.  with  potash ;  by  diazotizing 
(?-amido-benzoic  acid,  etc.,  etc.    For  other  methods,  see  p.  406. 

Freparation.  1 .  By  heating  sodium  phenate  in  a  stream  of 
carbonic  acid  at  180-200°  {Kolbe,  A.  113,  125;  115,  201,  etc), 
when  half  of  the  phenol  distils  over  and  basic  salicylate  of 
sodium  remains  behind : 

C6H40Na+C02  =  C6H4(OH).C02Na; 
CeH^(0H).C02Na  +  CeH,.0Na  =  C6H4(ONa).C02Na+CeH5.0H 


SALICYLIC  ACID,  ETC. 


421 


Should  potassium  phenate  be  used  instead  of  the  sodium  compound, 
salicylic  acid  is  likewise  formed  if  the  temperature  be  kept  low  (150°), 
but  the  isomeric  para- oxy benzoic  acid  at  a  higher  temperature  (220°). 
Neutral  salicylate  of  potassium,  C(5H4(OH).C02K,  decomposes  in  an 
analogous  manner  at  220°  into  phenol  and  basic  potassium  p-oxy- 
benzoate. 

2.  Sodium  phenate  is  heated  with  COg  in  a  closed  vessel  to  130°, 
when  neutral  salicylate  of  sodium  results,  [Schmitt,  B.  20,  Ref.  302), 
sodium  phenol-carbonate,  CgHg.O.COgNa,  being  formed  here  as  inter- 
mediate product. 

Salicylic  acid  crystallizes  in  colourless  four-sided  monoclinic 
prisms,  sparingly  soluble  in  cold  water  but  readily  in  hot ; 
M.  Pt.  155°.  It  can  be  sublimed,  but  breaks  up  into  phenol 
and  COg  when  heated  quickly ;  FegClg  colours  the  aqueous 
solution  violet.  It  is  an  important  antiseptic.  It  forms  two 
series  of  salts  (the  basic  calcium  salt  being  insoluble  in  water), 
and  two  series  of  derivatives,  viz.  :  (1)  as  an  acid  it  yields 
chlorides,  compound  ethers,  etc.,  and  (2)  as  a  phenol  it  yields 
a  methyl  ether,  etc.  e.g.  ethyl-salicylic  acid,  CgH4(O.C2H5)C02H. 
(Cf.  p.  382.) 

With  phenol  as  alcohol  there  results  Phenyl  salicylate, 
OH 

CqH.^<^qq  qq  jj  generally  termed  Salol,"  a  good  anti- 
septic, which  is  prepared  by  the  action  of  an  acid  chloride  such 
as  COClg  upon  a  mixture  of  salicylic  acid  and  phenol,  (B.  20, 
Ref  351).  It  forms  colourless  crystals.  When  its  sodium 
salt  is  heated  to  300°,  it  undergoes  molecular  transformation 
into  the  sodium  salt  of  the  isomeric  Phenyl-salicylic  acid, 

CaH.<g§;i^,  (B.  21,  501). 

m-Oxybenzoic  acid  is  prepared  by  diazotizing  m-amido- 
benzoic  acid.  It  crystallizes  in  microscopic  plates,  is  readily 
soluble  in  hot  water,  and  sublimes  without  decomposition ; 
FcgClg  does  not  colour  its  aqueous  solution. 

^-Oxybenzoic  acid  forms  monoclinic  prisms  ( -i-  HgO) ;  ferric 
chloride  gives  no  colouration  with  the  aqueous  solution. 

As  a  phenol  it  yields  the  methyl  ether,  Anisic  acid,  Cf^B^iO.  CH3).  CO.^H, 
which  can  be  prepared  by  treating  p-oxybenzoic  acid  with  methyl 
alcohol,  potash  and  methyl  iodide,  and  saponifying  the  dimethyl  ether 


422 


XXV.  AROMATIC  ACIDS. 


at  first  formed  ;  it  also  results  from  the  oxidation  of  aiiisol.  Beautiful 
rhombic  prisms.  In  consequence  of  the  phenolic  hydroxyl  having  been 
etherified,  it  resembles  the  monobasic  and  not  the  phenolic  acids, 
boiling— for  example— without  decomposition  ;  HI  and  HCl  break  it 
up  into  /)-oxybenzoic  acid  and  methyl  iodide  or  chloride.  For  its 
transformation  into  anisol,  see  p.  382. 

Acids  CgHgOg. 

;)-Oxy-phenyl-acetic  acid,  C(.H4(OH).CH2.C02H,  is  contained  in  urine 
and  has  also  been  noticed  as  a  product  of  the  decay  of  albumen.  Flat- 
shaped  needles.    Ferric  chloride  colours  its  solution  a  dirty  green. 

Acids  CgHjoOg. 

Hydro-ortho-cumaric  acid,  melilotic  acid,  C(3H4(OH)-CH2-CH2-C02H 
(I  :2),  occurs  in  melilotus  officinalis  and  results  from  the  reduction  of 
cumarin. 

The  isomeric  Hydro-para-cumaric  acid  (1  : 4)  is  produced 
by  the  decay  of  Tyrosine  (/3-oxyphenyl-alanine), 

C9H11NO3,  =  C6H4(OH)— OH2— CH(NH2)-C02H(1:4). 

Tyrosine,  which  crj^-stallizes  in  fine  silky  needles,  is  found  in 
old  cheese  (rv/ods),  in  the  pancreatic  gland,  in  diseased  liver, 
in  molasses,  etc.,  and  results  from  albumen,  horn,  etc.,  either 
upon  boiling  these  with  sulphuric  acid  or  from  their  pancreatic 
digestion  or  their  decay. 

It  has  been  obtained  synthetically,  (B.  15,  1545;  A.  219,  179). 
It  gives  a  violet  colouration  with  FcgClg  after  being  sulphurated  and 
neutralized.  Its  hydrochloride,  C9H11NO3.HCI,  crystallizes  in  large 
plates. 

4.  Alcohol-acids  and  Ketone-acids. 

The  monobasic  aromatic  alcohol-acids,  which  possess  at  one 
and  the  same  time  the  characters  of  acids  and  of  true  alcohols 
(p.  403),  contain  the  alcoholic  hydroxyl  in  the  side  chain  ;  this 
hydroxyl  is  consequently  eliminated  together  with  the  side 
chain  when  the  compound  is  oxidized. 


ALCOHOL-  AND  KETONE-ACIDS. 


423 


In  behaviour  they  approximate  very  nearly  to  the  alcohol- 
acids  of  the  fatty  series,  as  the  phenylated  derivatives  of  which 
they  thus  appear;  at  the  same  time  they  yield,  as  phenyl 
derivatives,  nitro-compounds,  etc.  (although  those  compounds 
can  often  not  be  prepared  directly,  on  account  of  the  ready 
oxidizability  of  the  alcohol-acids).  They  differ  from  the 
phenolic  acids  in  being  more  soluble  in  water,  less  stable, 
and  non-volatile ;  as  alcohols  many  of  them  give  up  HgO  and 
yield  unsaturated  acids  (which  the  phenolic  acids  can  never  do), 
and  they  can  be  etherified  by  HBr,  etc.  with  the  formation  of 
haloid-substitution  acids,  etc.  Further,  they  are  purely  mono- 
basic acids. 

The  alcohol-acids  may  be  either  primary,  secondary  or  tertiary  (see 
p.  209).  The  tertiary  can  sometimes  be  prepared  directly  by  the 
oxidation  of  such  acids  CnH2u-802  as  contain  a  tertiary  hydrogen  atom 
(^CH),  by  means  of  KMn04. 

To  the  ketonic  acids  the  corresponding  reactions  apply.  As  ketones 
they  are  reducible  to  alcohols,  the  above  (secondary)  alcohol-acids,  and 
they  further  react  with  hydroxylamine,  etc.  ;  as  acids  they  likewise 
form  compound  ethers,  etc. 

Polybasic  alcohol-acids,  etc.  are  of  course  also  theoretically  possible ; 
likewise  phenolic  alcohol-acids  (which  are  at  the  same  time  phenol 
and  alcohol-acid),  and  so  on.    Some  of  these  are  known. 


1.  Mandelic  Sicid,  phenyl-glycoUic  acid,  CgH5-CH(OH)-C02H, 
(1835),  results  upon  heating  amygdalin  with  hydrochloric 
acid,  and  synthetically  upon  saponifying  benzaldehy de-cyan- 
hydrin,  CgHs-CHlOH^CN,  (see  pp.  398  and  133).  Glancing 
crystals,  rather  easily  soluble  in  water;  M.  Pt.  133°. 

Mandelic  acid  exists  in  several  optically  different  modifications,  viz. , 
dextro-,  Isevo-,  and  inactive  or  para-mandelic  acid,  (cf.  B.  16,  1565 
and  2721).  It  is  comparable  with  lactic  acid,  CH3— CH(OH)— CO2H, 
yielding,  like  the  latter,  formic  acid  (together  with  benzoic)  upon 
oxidation ;  hydriodic  acid  reduces  it  to  phenyl-acetic  acid,  just  as 
it  does  lactic  acid  to  propionic. 

Hydrindic  acid,  C6H4(NH2)— CH(OH)— COgH,  whose  lactams  is 
dioxindole  (p.  434),  is  an  o-amido-mandelic  acid. 

2.  o-Oxymethyl-benzoic  acid,    ^(i^4,^co\)TT  '  which  is  isomeric 


424 


XXV.  AROMATIC  ACIDS. 


with  mandelic  acid,  is  unstable  in  the  free  state ;  as  an  ortho-com- 
pound, it  readily  goes  into  its  intra-molecular  anhydride  Phthalide, 

CqR^<^qq^^O,    The  latter  is  a  5-lactone  (see  p.  218),  and  results 

from  the  reduction  of  phthalic  acid  or  its  chloride.  It  crystallizes  in 
needles  or  plates  and  can  be  sublimed  unaltered. 

3.  Tropic  acid,  CgHjoOg,  =  CgHg— CH<^q        (needles  or  plates), 

is  obtained  together  with  tropine  by  boiling  atropine  with  baryta  water  ; 
it  is  reconverted  into  atropine  when  warmed  with  tropine  and  hydrochloric 
acid.  It  is  an  a-phenyl-/3-oxypropionic  acid.  The  a-compound  of  the 
phenyl-a-propionic  acids  is  Atro-lactinic  acid,  CH3-CH(OH)(C6H5)-C02H 
(which  can  be  prepared  from  atropic  acid),  and  the  /3-acid  is  Phenyl- 
lactic  acid,  CgHg-  CHa— CH(OH)— COgH ;  the  latter  stands  in  the 
same  relation  to  cinnamic  acid  as  lactic  acid  does  to  acrylic. 

4.  Benzoyl-formic  Sioid,  phenyl-glyoxylic  acid,  CgH^-CO-COgH, 
is  obtained  synthetically  by  saponifying  benzoyl  cyanide, 
C^^Hg.CO.CN,  with  cold  fuming  HCl  {Claisen,  1877),  and  also 
by  the  cautious  oxidation  of  mandelic  acid.  It  is  an  oil  which 
only  solidifies  slowly,  and  which  breaks  up  in  great  part  into 
CO  and  CgHg.COgH  when  distilled.  It  reacts  similarly  to 
isatin  with  benzene  containing  thiophene  and  sulphuric  acid, 
and  shows  the  normal  reactions  of  the  ketonic  acids  with 
NaHSOg,  HON,  NH2.OH,  etc. 

o-Nitro-benzoyl-formic  acid,  C6H4(N02) — CO — COgH,  which  can  be 
prepared  from  o-nitro-benzoyl  cyanide,  yields  o-Amido-benzoyl-formic 

acid,  isatic  acid,  CqH.4<^qq^qq  U  (a  white  powder)  upon  reduction ; 

when  a  solution  of  the  latter  is  warmed,  it  goes  into  its  intramolecular 

anhydride  (lactime),  isatin,  C(3H4<^qq'^^  (OH)  ^' 

5.  Benzoyl-acetic  acid,  CgHg— CO — CHg — CO2H  (Baeyer),  is  a  perfect 
analogue  of  aceto-acetic  acid  and,  like  the  latter,  can  be  used  for  the 
most  various  syntheses.  It  is  obtained  as  ethyl  ether  (which  is  soluble 
in  a  cold  solution  of  soda),  by  dissolving  phenyl-propiolic  ethyl  ether 
in  concentrated  sulphuric  acid  and  pouring  the  solution  into  water, 
(B.  16,  2128) ;  or,  better,  by  the  action  of  sodium  ethylate  upon  a 
mixture  of  ethyl  benzoate  and  acetate  (B.  20,  651).  It  is  crystalline 
and  melts  at  85-90°  ;  the  aqueous  solution  is  coloured  a  beautiful  violet 
by  FegClg.  It  readily  gives  up  COg  and  goes  into  aceto-phenone, 
C6H5--CO-CH3. 


PROTOCATECHUIC  ACID;  GALLIC  ACID.  425 


5.  Tri-  and  polyatomic  monobasic  Phenolic  Acids. 

Dioxy-henzoic  acids,  CgH3(OH)2C02H. 

1.  Protocatechuic  acid,  (CO^HiOHiOH  =  1:3:4),  is 
obtained  b}^  fusing  various  resins  such  as  catechu,  benzoin 
and  kino,  with  alkali.  It  may  be  prepared  synthetically  e.g. 
(together  with  the  acid  1:2:3)  by  heating  pyrocatechin, 
CgH4(OH)2,  with  carbonate  of  ammonia.  It  crystallizes  in 
glancing  needles  or  plates  and  is  readily  soluble  in  water ; 
the  solution  is  coloured  green  by  ferric  chloride,  then — after 
the  addition  of  a  very  little  Na2C03 — blue,  and  finally  red. 
Like  pyrocatechin  it  possesses  reducing  properties.  Its  mono- 
methyl  ether  is  : 

VaniUic  acid,  C6H3(C02H)(0,CH3)(OH),  which  results  from  the 
oxidation  of  vanillin  (p.  401) ;  its  dimethyl  ether  is  the  Veratric  acid  of 
sabadilla  seed  (Veratrum  Sabadilla) ;  and  its  methylene  ether  is  Piper- 
onylic  acid,  which  can  be  prepared,  among  other  methods,  by  the  oxida- 
tion of  piperic  acid  (p.  427). 

Hydroquinone-carhoxylic  acids. 

The  carboxylic  acids  of  hydroquinone,  which  are  convertible  into 
carboxylic  acids  of  quinone,  are  dioxy-benzoic  acids  which  contain  both 
hydroxyls  in  the  para-position. 

2.  Quinone-tetrahydro-carboxylic  acid,  C6H3.H4.(02)(C02H)  (A.  211, 
306),  is  a  hydro-derivative  of  Quinone -carboxylic  acid,  C6H3(02).C02H. 

3.  Among  the  homologues  of  the  above  may  be  mentioned  Orsellinic 
acid,  C8H8O4,  =:  C6H2(CH3)(OH)2(C02H),  which  is  found  in  various 
lichens,  its  erythritic  ether,  erythrin  (p.  203),  also  occurring  in  these 
(in  Rocella  fusiformis).  Orsellinic  acid  is  the  type  of  a  series  of  analog- 
ous acids,  the  so-called  lichen  acids. 

Trioxy-henzoic  acids, 

Gallic  acid,  C^H,0„  =  C6H2(OH)3(C02H),  [C02H:(OH)3  - 
1:3:4:5],  occurs  in  nutgalls,  in  tea  and  many  other  plants, 
and  as  glucoside  in  several  tannins.  It  is  prepared  by  boiling 
tannin  with  dilute  acids  or  by  allowing  mould  to  form  on  its 
solution,  and  has  also  been  got  synthetically  by  various 
reactions.    It  crystallizes  in  fine  silky  needles  (+  H2O),  is 


426 


XXV.  AROMATIC  ACIDS. 


readily  solul)le  in  water,  alcohol  and  ether,  and  has  a  faintly 
acid  and  astringent  taste.  It  gives  up  COg  and  goes  into 
pyrogallol  when  heated,  reduces  gold  and  silver  salts,  and 
yields  a  bluish-black  precipitate  with  ferric  chloride.  Like 
pyrogallic  acid,  it  is  very  readily  oxidized  in  alkaline  solution, 
with  the  production  of  a  brown  colour. 

Among  its  isomers  is  Pyrogallol-carboxylic  acid  (1:2:3:4). 

Tannin,  gallotanic  acid,  ^iJ^io^g  +  ^HgO,  is  a  colourless 
amorphous  glancing  mass,  readily  soluble  in  water  but  only 
slightly  in  alcohol,  and  almost  insoluble  in  ether.  It  forms 
the  chief  constituent  of  nutgalls,  and  is  likewise  present  in 
sumach,  tea,  etc.  It  goes  into  gallic  acid  when  boiled  with 
dilute  acids,  being  conversely  obtained  from  the  latter,  e.g.  by 
means  of  POCI3,  with  separation  of  water  : 

2C,H,05  =  Ci.HioOg  +  H,0. 

The  aqueous  solution  is  coloured  dark  blue  by  ferric 
chloride.  Tannin  has  an  affinity  for  the  animal  skin  and  for 
glue,  and  is  abstracted  from  its  solution  by  these  substances, 
the  skin  being  thus  tanned  or  converted  into  leather. 

Analogous  to  tannin  in  this  latter  respect  are  a  number  of  other 
tannic  acids,  viz.  Kino-tannic  acid,  Catechu-tannic  acid  (in  Mimosa 
catechu),  Morin-tannic  acid  (in  Morus  tinctoria),  Caffetannic  acid,  Oak- 
tannic  acid  (in  oak  bark),  Cinchona-tannic  acid  (in  cinchona  bark),  etc. ; 
the  composition  of  these  is  for  the  most  part  complicated,  since  the 
larger  number  of  them  are  glucosides  (p.  512),  i.e.  ethers  of  tannic  acid 
with  glucoses,  and  consequently  break  up  into  gallic  acid  and  the  sugar 
when  boiled  with  dilute  acids.  They  are  characterized  by  their  great 
solubility  in  water,  harsh  astringent  taste,  affinity  for  the  animal  skin, 
and  also  by  the  intense  colourations  they  give  with  ferrous  or  ferric 
salts,  as  well  as  by  the  fact  of  their  being  precipitated  by  a  solution  of 
lead  acetate. 

Tetroxy-henzoic  acids. 

Quinic  acid,  C7Hi20g,  which  is  found  in  quinine  bark,  coffee  beans, 
etc.,  is  a  hexahydro-tetroxy-benzoic  acid,  C6H.Hg.(OH)4C02H.  It 
crystallizes  in  colourless  prisms. 


OXY-CINNAMIC  ACIDS. 


427 


6.  Unsaturated  monobasic  Phenolic  Acids. 

Oxy-cinncmic  acids. 
OH 

Cumaric  acids,  CJ6H4<Cqh=CH— COgH 

o-Cumaric  acid  is  present  in  melilot  (Melilotus  officinalis),  and  can 
be  prepared  by  diazotizing  o-amido-cinnamic  acid,  or  from  salicylic 
acid  by  the  Perkin  reaction.  It  also  results,  as  potassium  salt,  on  dis- 
solving its  intra-molecular  anhydride,  cumarin,  in  concentrated  potash 
solution.  Long  needles,  which  decompose  upon  fusion  and  are  readily 
soluble  in  water  and  alcohol.  The  alcoholic  solution  is  yellow  with  a 
green  fluorescence. 

Cumarin  or  cumaric  anhydride,  CqH.^<^^  is  the 

aromatic  principle  of  woodward  (Asperula  odorata),  and  is  also 
found  in  the  Tonka  bean  and  other  plants.  It  is  obtained  by 
the  elimination  of  HgO  from  o-cumaric  acid,  e.g.  by  means  of 
acetic  anhydride.  For  its  formation  from  phenol  by  means  of 
malic  acid  etc.,  see  p.  409.  Glancing  prisms,  readily  soluble 
in  alcohol,  ether  and  hot  water ;  M.  Pt.  67°,  B.  Pt.  290\ 

With  regard  to  isomerism  in  the  cumaric  acid  series,  see  Fittig, 
A.  216,  119,  170. 


Dioxy-cinnamic  acids. 
To  this  group  belong  Caffeic  acid, 

C9H8O4,  =  C6H3(OH)2-(CH=CH— CO2H) 
(yellow  prisms,  from  cafFetannic  acid),  whose  mono-methyl  ether  is 
Ferulic  acid  (from  asafoetida) ;  further,  the  isomeric  Umbellic  acid  or 
/)-oxy-o-cumaric  acid,  which  readily  changes  into  the  anhydride  corre- 
sponding to  cumarin,  viz.,  UmlDelliferone,  CyHgOg ;  this  last-named 
compound  is  present  in  varieties  of  Daphne. 
Related  to  the  above  is  Piperic  acid  : 

C'6H3(o>CH2)  .CH-CH-CH^CH-CO^H, 

a  decomposition  product  of  piperine  (p.  488),  which  crystallizes  in  long 
needles. 


428 


XXV.  AROMATIC  ACIDS. 


Trioxy-cinnamic  acids. 
0  —CO 

^sculetin,  C6H2{OH)2<^^jj_^^jj,  and  its  isomeride  Daplmetin  are 

dioxy-cumarins,  their  glucosides  (/Esculin  and  Daphnin)  occurring 
respectively  in  the  horse  chestnut  and  in  Daphne  varieties.  Like  the 
dioxy-cinnamic  acids  they  may  also  be  prepared  synthetically,  (B.  17, 
2191). 


B.  Dibasic  Acids. 

The  dibasic  acids  occupy  exactly  the  same  position  in  the 
aromatic  series  as  the  dibasic  acids  Ci,H2n_204  do  in  the  fatty ; 
they  form  two  series  of  each  derivative  (compound  ethers, 
chlorides,  amides,  etc.).  The  two  carboxyl  groups,  which 
according  to  theory  they  contain,  may  either  both  be  in 
the  nucleus  or  in  the  side  chain  or  chains,  or  be  divided 
between  them.  Dibasic  phenolic  acids  can  of  course  occur 
here  also. 


Benzene-dicarboxylic  acids^  CgH4(C02H)2. 

1.  Phthalic  acid,  GQii^iCO^Il)^  (1  :  2),  (Laurent,  1836), 
results  when  any  o-di-derivative  of  benzene,  which  contains 
two  carbon  side  chains,  is  oxidized  by  HNO3  or  KMnO^,  but 
not  CrOg  (cf.  p.  326) ;  it  is  formed  in  especial  by  the  oxidation 
of  naphthalene  by  nitric  acid,  and  also  of  anthracene  deriva- 
tives. In  preparing  it  on  the  large  scale  the  naphthalene  is 
first  converted  into  its  tetra-chlor-addition  product,  C^oHgCl^, 
and  this  then  oxidized.  It  crystallizes  in  short  prisms  or 
plates,  M.  Pt.  184°,  readily  soluble  in  water,  alcohol  and  ether. 
When  heated  above  its  melting  point,  it  goes  into  the  anhy- 
dride (see  below).  It  loses  one  mol.  COg  when  heated  with  a 
little  lime,  and  two  mols.  when  heated  with  excess,  yielding 
benzoic  acid  or  benzene.  Chromic  acid  disintegrates  it  com- 
pletely, while  sodium  amalgam  converts  it  into  hydro-phthalic 
acid,  CgH4.H2.(C02H)2.  Its  barium  salt,  CgH^(C02)2Ba,  is 
difficultly  soluble  in  water. 


PHTHALIC  AND  OXY-PHTHALIC  ACIDS. 


429 


Phthalic  anhydride,  GqH^<^^q^O,  crystallizes  in  magni- 
ficent long  prisms  which  can  be  sublimed ;  M.  Pt.  128°,  B.  Pt. 
284°.  It  is  used  in  the  preparation  of  eosin  dyes  (see 
fluorescein). 

The  chloride,  Phthalyl  chloride,  which  results  from  the 
action  of  PCI5  upon  the  acid,  appears  strangely  enough  not  to 

have  the  constitution  06H4(OOCl)2  but  that  of  C6H4<^q  2\.o, 

as  it  yields,  for  instance,  phthalo-phenone,  CgH^ 

with  benzene  and  Al2Clg.  Sodium  amalgam  transforms  it  into 
phthalide. 

2.  Isophthalic  acid  (1:3)  crystallizes  in  fine  long  needles 
from  hot  water,  in  which  it  is  only  sparingly  soluble  ;  it 
sublimes  without  forming  an  anhydride,  and  is  reduced  by 
nascent  hydrogen  to  tetrahydro-isophthalic  acid.  The  barium 
salt  is  readily  soluble  in  water. 

3.  Terephthalic  acid  (1:4)  results  from  the  oxidation  of 
jp-xylene,  cymene  etc.,  and  especially  of  oil  of  turpentine  or 
oil  of  cumin.  It  forms  a  powder  almost  insoluble  in  alcohol 
and  water,  and  sublimes  unchanged.  Nascent  hydrogen  con- 
verts it  into  tetra-  and  hexahj^dro-terephthalic  acids.  The 
barium  salt  is  only  sparingly  soluble. 

A  large  number  of  substitution  products  of  the  phthalic  acids  are 
known,  e.g.  chloro-  and  bromo-phthalic  acids  (which  are  used  in  the 
eosin  industry),  nitro-,  amido-,  oxy-  and  sulpho-phthalic  acids,  etc. 


Oxy-phthalic  Acids, 

The  six  Oxy-phthalic  acids,  C6H3(OH)(C02H)2,  are  of  theoretical 
interest,  (cf.  p.  .314). 

Dioxy-terephthalic  acid,  hydroquinone-p-dicarboxylic  acid,  C8H(.0(5, 
=  C6H2(OH)2(C02H)2,  in  which  both  the  hydroxyls  and  the  carboxyls 
are  respectively  in  the  p-position  to  one  another,  results  as  ethyl 
ether  by  the  action  of  bromine  upon  succino-succinic  ether,  or  of 
sodium  ethylate  upon  dibromo-aceto-acetic  ether.  The  free  acid  breaks 
up  into  hydroquinone  and  CO2  when  distilled,  and  is  converted  by 


430 


XXV.  AROMATIC  ACIDS. 


nascent  hydrogen  into  siiccino-succinic  acid,  i.e.  the  benzene  nucleus  is 
reduced"  to  a  hexa-methylene  derivative.  Succino- succinic  ether, 
whose  constitution  is  given  on  p.  .320,  crystallizes  in  triclinic  prisms 
which  melt  at  126°,  and  dissolve  in  alcohol  to  a  bright  blue 
fluorescent  liquid  which  is  coloured  cherry-red  by  ferric  chloride. 
It  contains  two  replaceable  H -atoms  (in  the  methine  groups), 
being  analogous  to  aceto-acetic  ether.  The  free  acid  changes,  on 
losing  COg,  into  quinone-tetrahydro-carboxylic  acid,  formerly  termed 
succino-propionic  acid  (see  p.  425),  and  then  into  quinone-tetrahydride, 

^^<^Ch'— CH^^^^  (colourless  prisms,  M.  Pt.  75°;  A.  211,  322). 

Succino-succinic  acid  and  many  of  its  derivatives  behave  partly  as 
quinones  and  partly  as  phenols,  and  are  sometimes  coloured  (yellow 
or  yellow-green),  sometimes  colourless.  Certain  relations  have  been 
made  out  between  behaviour  and  colour  which  are  of  service  in  drawing 
conclusions  as  to  the  constitution  of  the  compounds  in  question.  The 
phenomenon  of  desmotropism  (p.  266)  has  been  closely  investigated 
here,  (B.  20,  2801). 

Hemipinic  acid  is  a  dimethyl  ether  of  the  isomeric  pyrocate- 
chin-o-dicarboxylic  acid,  while  the  half-aldehyde  of  the  latter  is 
Opianic  acid,  and  the  corresponding  alcohol-acid  is  Meconinic  acid 
C6H2(O.CH3)2(C02H)(CH2.0H) ;  all  these  compounds  are  nearly  related 
to  pyrocatechuic  acid  and  can  be  prepared  from  narcotine.  For  the 
constitution  of  opianic  acid,  of.  also  B.  19,  2275. 


0.  Tri-  to  Hexabasic  Acids. 

Benzene-fricarboxylic  Acids,  CgH3(C02H)3. 

1.  Trimesic  acid  (1:3:5).    From  mesitylene. 

2.  Trimellitic  acid  (1:2:4).    From  colophonium. 

3.  Hemimellitic  acid  (1:2:3). 

Benzene-tetracarhoxylic  Acids,  CgH2(C02H)4. 

1.  Pyromellitic  acid,  2.  Prehnitic  acid,  3.  Mellophanic  acid. 

The  above  six  acids  have  been  prepared  from  mellitic  acid  or  its 
hydro-derivatives  by  the  partial  separation  of  CO2.  They  readily  yield 
(tetra-)  hydro-acids  with  sodium  amalgam. 

4.  Hydroquinone-  and  quinone-tetracarboxylic  acids.  See  B.  19, 
516. 


INDIGO  GROUP;  INDIGO.  431 

Benzene-;pentacarhoxylic  Acid,  CgH(C02H)5. 

Only  one  modification  is  theoretically  possible  and  only  one  is 
known. 

Benzene-hexacarhoxylic  Acid,  Cg(C(32H)g. 

Mellitic  acid,  Ci2HgOj2>  occurs  in  peat  as  aluminium  salt  or 
honey-stone,  G^^kl^O^^^  which  crystallizes  in  octahedra,  and  it 
results  from  the  oxidation  of  lignite  or  graphite  with  KMnO^. 
It  forms  fine  silky  needles  of  great  stability.  It  can  neither  be 
chlorinated,  nitrated  nor  sulphurated,  but  is  readily  reduced 
by  sodium  amalgam  to  Hydromellitic  acid,  G-^^^^fi^^,  and 
yields  benzene  when  distilled  with  lime. 

XXVI.  INDIGO  (OR  INDOLE)  GROUP. 

(Cf.  the  arrangement  of  Baeyer's  researches,  which  are  cited  below, 
in  R.  Meyer's    Theerfarbstoffe,"  Vieweg  und  Sohn.) 

Indigo,  which  is  obtained  from  the  indigo  plant  (Indigofera 
tinctoria),  and  from  woad  (Isatis  tinctoria),  has  been  known 
for  thousands  of  years  as  a  valuable  blue  dye,  especially  for 
woollen  fabrics.  In  addition  to  indigo  blue  (indigotin), 
commercial  indigo  contains  indigo-gelatine,  indigo-brown  and 
indigo-red,  all  of  which  can  be  extracted  from  it  by  solvents. 
The  colouring  matter  is  not  present  as  such  in  the  indigo  plant, 
but  as  the  glucoside  "  Indican,"  from  which  it  can  be  separated 
either  by  dilute  acids  or  by  the  action  of  the  air  in  presence  of 
water. 

It  forms  a  dark  blue  coppery  and  shimmering  powder  or, 
after  sublimation,  copper-red  prisms,  insoluble  in  most  solvents 
(including  the  alkalies  and  dilute  acids),  but  dissolving  to  a 
blue  solution  in  hot  aniline  and  to  a  red  one  in  paraffin,  from 
either  of  which  it  may  be  crystalhzed.  Its  vapour  is  dark  red. 
The  formula  CigH^QN202  is  confirmed  by  the  vapour  density. 
It  is  converted  by  reducing  agents,  such  as  ferrous  sulpliate 
and  caustic  soda  solution  or  grape  sugar  and  soda,  into  Indigo 


432 


XXVI.  INDIGO  GROUP. 


white,  CigH^2-^2^2'  ^  white  crystalline  powder  soluble  in 
alcohol  and  ether,  also  in  alkalies  and  in  phenol ;  the  alkaline 
suhition  quickly  becomes  oxidized  by  the  oxygen  of  the  air, 
with  the  separation  of  a  blue  film  of  indigo.  It  yields  an 
acetyl  compound  which  crystallizes  in  colourless  needles. 

Warm  concentrated  or  fuming  sulphuric  acid  dissolves 
indigo  to  Indigo-mono-sulphonic  and  di-sulphonic  acids,  the 
former  of  which  (termed  phoenicin-sulphonic  acid)  is  difficultly 
soluble  in  water  but  the  latter  readily  so ;  the  sodium  di- 
sulphonate  is  the  indigo  carmine  of  commerce.  Nitric  acid 
oxidizes  indigo  to  isatin,  while  distillation  with  potash  yields 
aniline,  and  heating  with  manganese  dioxide  and  a  solution  of 
potash,  anthranilic  acid. 

Indigo  has  been  prepared  synthetically  by  Baeyer,  (B.  14, 
1741;  15,  775,  2093,  2856;  16,  1704,  2188,  etc.). 

1.  From  isatin  chloride. 

2.  By  warming  o-nitro-phenyl-propiolic  acid  with  (e.g.)  grape 
sugar  in  alkaline  solution  : 

2C6H4(N02)C=C.C02H  +  2H2  -  CigHioN202+ 2CO2  + 2H2O. 

3.  From  o-nitro-phenyl-acetylene  (p.  332),  by  converting  it  into 
o-dinitro-diphenyl-diacetylene,  C6H4(N02)C=C— C=C— C6H4(N02)  (p. 
459),  treating  the  latter  with  H2SO4,  and  finally  reducing. 

4.  By  the  action  of  dilute  alkalies  upon  a  solution  of  o-nitro- 
benzaldehyde  in  acetone : 

2C6H4(N02)CHO  +  2C3H60  =  C^,R^,-Nfi^  +  2G^}ifi^  +  2}ifi. 

There  is  formed  as  intermediate  product  in  this  reaction  **o-nitro- 
phenyl-lacto-methyl-ketone,"C6H4(N02)— CH(OH)— CH2— CO— CH3. 

5.  By  the  oxidation,  etc.,  of  indoxylic  acid  and  indoxyl. 

The  constitution  of  indigo  is  very  probably  : 

The  following  are  isomerides  of  indigo  :  indigo  red  (in  the  indigo  of 
commerce),  indirubin  (also  called  indigo-purpurin),  and  indin ;  the  last 
two  of  these  have  been  prepared  synthetically. 

There  have  also  been  prepared  dichlor-,  dibrom-,  tetrachlor-,  diethyl-. 


ISATIN. 


433 


etc.  substitution  products  of  indigo,  also  indigo-carboxylic  acid,  (B.  12, 
458). 


Derivatives  of  Indigo. 


CoH.NO. 

C6H4<^>C(OH) 

C6H4<QH(QU)>CO 

<^6H4<Q(OH)^^^ 

C6H4<gg>CH 

C8He(CH3)N 

(and  its  isomers) 

1.  Isatin,  CgH4<^QQ^0(OH),is  easily  prepared  by  oxidizing 

indigo  with  nitric  acid  {Erdmann  and  Laurent,  1841 ;  cf. 
also  B.  17,  976).  It  likewise  results  from  the  oxidation  of 
dioxindole,  of  oxindole  (indirectly),  and  of  indoxyl  (Baeyer)  \ 
also  by  boiling  o-nitro-phenyl-propiolic  acid  with  alkalies. 
It  crystallizes  in  reddish-yellow  monoclinic  prisms,  which 
are  only  sparingly  soluble  in  cold  water,  but  more  readily  in 
hot  water  and  in  alcohol  to  a  brownish-red  solution.  Caustic 
potash  dissolves  it  at  first  to  a  violet  solution,  with  the 
formation  of  the  compound  CgH^NO.OK,  but  this  changes 
into  potassium  isatate,  CgH4(NH2) — CO — COOK,  upon  warm- 
ing (p.  424).  Isatin  is  the  lactime  of  isatic  acid  (o-amido- 
benzoyl-formic  acid),  (p,  416). 

For  its  synthesis  from  o-nitro-benzoyl-formic  acid,  see  p.  424,  and 
for  its  reaction  with  thiophene,  p.  298.     Chloro-,  Bromo-  and  Nitro- 
isatins  are  also  known.    As  a  ketone,  isatin  forms  with  ammonia 
Imesatin,  CgHgNOlNH)",  by  the  exchange  of  O  for  NH ;  and  with 
( 506 )  2  E 


434 


XXVI.  INDIGO  GROUP. 


hydroxylamine,  Isatoxime,  C6H4<^Qj_jq.  qjjj^C.OH  (yellow  needles), 

which  also  results  from  oxindole  and  nitrous  acid.  The  homologous 
Methyl-isatin  can  be  obtained  from  p-toluidine  and  dichlor-acetic  acid, 
a  tolyl  derivative  of  Methyl -ime satin  being  formed  here  in  the  first 
instance,  (B.  18,  190).     Chromic  acid  oxidizes  isatin  to  Isatoic  acid 

CO 

(anthranil-carboxylic  acid),  CsHgNOg,  =  C6H4<^  •  (cf.  p.  414). 

^ — 002tL 

Isatin  yields  a  methyl  ether,  Methyl-isatin,  C6H4<^^^C.  0.  CHg, 

which  is  prepared  from  isatin-silver  (a  red  powder)  and  methyl  iodide, 
and  forms  blood-red  crystals ;  it  dissolves  in  alkali  to  isatic  acid  and 
methyl  alcohol,  i.e.  the  water  abstracted  in  the  formation  of  lactime  is 
again  taken  up,  and  the  methyl  ether  is  saponified.  From  this  reaction 
the  above  constitutional  formula  of  isatin  follows. 

An  isomeric  compound,  Methyl-pseudo -isatin,  is  derived  from  an 
unknown  isomer  of  isatin,  pseudo-isatin,  C6H4<^qq^CO,  the  lactame 

of  amido-benzoyl-formic  acid.  This  results  e.g.  by  the  action  of 
sodium  hypobromite  upon  methyl-indole  and  subsequent  boiling 
with  alcoholic  potash ;  since  it  dissolves  at  once  in  alkali  to  Methyl- 
isatic   acid,    C6H4(NH.CH3) — CO — CO2H,    it   has    the  constitution 

C6H4<^gJ^3)>cO,  (B.  17,  559). 

CO 

Isatin  chloride,  C6H4<^    ^C.  CI  (from  isatin  and  PCI5),  crystallizes 

in  brown  needles  which  are  soluble  in  alcohol  and  ether  with  a  blue 
colour.  It  goes  into  indigo  when  treated  with  hydriodic  acid,  or  with 
zinc  dust  and  glacial  acetic  acid  (synthesis  of  indigo,  Baeyer) : 

2C8H4NOCI  +  2H2  =  C16H10N2O2  +  2HC1. 

2.  Dioxindole^  C6H4<^^'^^"^'^CO,  is  the  intra-molecular  anhydride 

of  the  unstable  o-amido-mandelic  acid  (p.  423).  It  is  obtained  from 
the  reduction  of  isatin  (into  which  it  is  again  easily  oxidized)  with 
zinc  dust  and  hydrochloric  acid.  Readily  soluble  colourless  prisms, 
M.  Pt.  180°.  It  possesses  both  basic  and  acid  properties  (two  H-atoms 
being  replaceable),  and  forms  a  nitroso-compound,  acetyl  derivative 
(the  acetyl  being  joined  to  the  N),  etc. 

TVTTT 

3.  Oxindole,  CgH4<^Qjj  ^CO,  the  lactame  of  (?-amido- 

phenyl-acetic  acid,  is  formed  by  the  reduction  of  o-nitro- 
phenyl- acetic  acid  (p.  416);  also  by  that  of  dioxindole  with 
tin   and    hydrochloric    acid.      Colourless    needles,  readily 


OXINDOLE  ;  INDOXYL. 


435 


oxidizable  to  dioxindole,  and  therefore  of  faintly  reducing 
character.  Oxindole  is  at  the  same  time  an  acid  and  a 
base,  dissolving  both  in  alkalies  and  in  hydrochloric  acid. 
Baryta  water  at  a  somewhat  high  temperature  transforms  it 
into  ^?-amido-phenyl-acetate  of  barium.  The  imido-hydrogen 
is  exchangeable  for  ethyl,  acetyl,  the  nitroso-group,  etc. 
4.  Isomeric  with  oxindole  is  : 

Indoxyl,  CgH4<^Q^Qjj^^CH,  which  is  obtained  by  the 

separation  of  COg  from  indoxylic  acid,  and  which  is  often 
present  in  the  urine  of  the  carnivora  as  potassium  indoxyl- 
sulphate  or  urine-indican,  CgHgN.0.(S03K).  It  is  a  thick 
liquid,  moderately  soluble  in  water  with  yellow  fluorescence, 
and  not  volatile  with  steam. 

It  dissolves  in  concentrated  hydrochloric  acid  to  a  red  solution.  It 
is  very  unstable,  quickly  becoming  resinous,  and  readily  changing  into 
indigo  when  its  ammoniacal  solution  is  exposed  to  the  air,  or  when 
ferric  chloride  is  added  to  its  solution  in  hydrochloric  acid. 

It  yields  a  Nitroso-compound,  C6H4<^q^^^^^^CH,  of  the  same 

character  as  the  nitrosamines,  and  therefore  it  contains  an  imido- 
group ;  further,  its  relation  to  indoxyl -sulphuric  acid  shows  that  it 
contains  an  alcoholic  hydroxyl,  from  which  its  constitution  follows. 

Potassium  indoxyl- sulphate  is  prepared  synthetically  by  warming 
indoxyl  with  potassium  pyrosulphate  ;  it  crystallizes  in  glancing  plates 
and  breaks  up  again  backwards  when  warmed  with  acids. 

Ethyl-indoxyl  results  from  indoxyl  by  the  exchange  of  the  hydroxylic 
hydrogen  for  CgHg.    Derivatives  of  the  hypothetical  Pseudo-indoxyl, 

C6H4<^^Q^CH2,  are  also  known,  some  of  them  being  convertible  into 

indigo  derivatives  (e.g.  diethyl-indigo). 

Indoxylic  acid,  C6H4<^^|q jj^^C— COgH,  the  carboxylic  acid  of 

indoxyl,  forms  white  crystals,  is  converted  into  indigo  by  ferric  chloride, 
and  breaks  up  into  indoxyl  and  COg  when  fused.  It  is  obtained  from 
its  ether  : 

Ethyl  indoxylate,  by  fusing  with  soda.  The  latter  compound,  which 
crystallizes  in  thick  prisms,  M.  Pt.  120°,  also  results — among  other 
methods  — from  the  reduction  of  ethyl-o-nitro-phenyl-propiolate  with 
ammonium  sulphide. 

The  mother  substance  of  the  whole  indigo  group  is  : 


436 


XXVI.  INDIGO  GROUP. 


5.  Indole,  C6H4<§2>CH  {Baeyer,  1868),  which  is  ob- 
tained by  distilling  oxindole  with  zinc  dust;  by  heating 
o-nitro-cinnamic  acid  with  potash  and  iron  filings ;  by  the 
action  of  sodium  alcoholate  upon  o-amido-chloro-styrene  (from 
(?-nitro-cinnamic  acid  +CIOH-CO2)  (B.  17,  1067): 

C6H4<^^!^(.jj(.l  +  NaO.C2H5  =  C6H4<^^>CH  +  NaCl  +  C2H5OH  ; 

by  the  pancreatic  fermentation  of  albumen;  together  with 
skatole  by  fusing  albumen  with  potash;  and  by  passing  the 
vapours  of  various  anilines,  e.g.  diethyl-o-toluidine,  through 
red-hot  tubes,  etc.  It  crystallizes  in  glancing  plates,  M.  Pt. 
52°,  volatilizes  readily  with  steam,  and  has  a  peculiar  faecal- 
like  odour.  It  is  weakly  basic,  colours  a  pine  shaving  which 
has  been  moistened  with  HCl  cherry-red,  gives  a  red  precipi- 
tate of  nitroso-indole  with  N2O3  (a  delicate  reaction),  and 
yields  acetyl-indole  when  acetylated.  These  last  reactions 
show  that  indole  contains  an  imido-group. 

Indole  may  be  looked  upon  as  pyrrol  which  has  two  C-atoms  in 
common  with  a  benzene  nucleus,  as  in  the  case  of  naphthalene : 
NH  CH 

(a)    Ch/\J/\cH  j^jj 
(/3)    ChLJ^^CH'  =  CeH<^jj>CH. 
CH 

A  large  number  of  derivatives  spring  from  indole  by  the  replacement 
either  of  the  imido-hydrogen,  or  of  the  hydrogen  atoms  marked  (a)  and 
(/3),  or  of  those  of  the  benzene  nucleus.  These  result  synthetically  e.g. 
by  the  condensation  of  the  aromatic  primary  or  secondary  hydrazines 
either  with  pyroracemic  acid  or  with  certain  ketones  or  aldehydes,  and 
treatment  of  the  resulting  hydrazides  with  dilute  HCl  or  ZnClg  [E. 
Fischer,  B.  17,  559 ;  19,  1563) ;  thus  acetone-phenyl-hydrazine,  for 

instance,  yields  a-methyl-ketole,  C^^<^q^^Q—CK^,  propyl  aldehyde- 
phenyl-hydrazine  yields  skatole,  and  so  on. 

Skatole,  p-methyl-indole,  ^6^4.'^(j,^qjj^  ^^CH,  is  found  in  faeces,  and 
is  produced  together  with  indole  e.g.  by  the  decay  of  albumen  or  by 
fusing  it  with  potash.  Colourless  plates  of  a  strong  faecal  odour, 
M.  Pt.  95°.  Nitrous  acid  does  not  colour  it  red.  It  takeii  up  two 
atoms  of  hydrogen  to  form  a  hydro-compound. 


DERIVATIVES  OF  INDOLE. 


437 


Methyl-indole,  CqH^<^^^^^^^^^CH,   results  from  phenyl-methyl- 

hydrazine  (p.  372)  and  pyroracemic  acid,  at  first  in  the  form  of  the 
carboxylic  acid.    It  is  an  oil,  B.  Pt.  239°. 

Just  as  furfurane  and  thiophene  are  related  to  pyrrol,  so  there  are 
compounds  analogous  to  indole  which  contain  oxygen  or  sulphur  in 
place  of  the  imido-group.    We  know,  for  example,  a  hydroxyl-deriva- 

S 

tive  of  Thio-naphthene,  CqR4<^qj^C1I  [a  compound  as  yet  but  little 

known,  (B.  19,  1432,  1667)],  viz.  Oxy-thio-naphthene  (B.  19,  1617), 

which  resembles  a-oxy-naphthalene  (a-naphthol)  in  the  same  degree  as 
thiophene  does  benzene.  Cf.  pp.  297  et  seq,  ;  also  B.  19,  1290,  1300, 
2927. 


The  compounds  of  the  aromatic  series  which  have  been 
treated  of  up  to  now  are  derived,  with  the  exception  of  indigo, 
from  one  molecule  of  benzene,  i.e.  they  contain  one  benzene 
nucleus.  There  are  however  a  vast  number  of  compounds 
known  which  contain  two  or  more  benzene  nuclei. 

1.  When  two  phenyl  groups  are  joined  together  directly, 
there  results  Di-phenyl,  GqR—GqH^  (Group  XXVII.). 

2.  When  a  methylene  group,  i.e,  a  carbon  atom,  connects  two 
phenyl  groups,  we  obtain  Diphenyl-methane,  CqH.^ — CHg — CgH^ 
(Group  XXVIII. ). 

3.  Should  three  benzene  residues  be  joined  in  a  similar 
manner  to  methine,  Triphenyl-methane,  ^{(GqR^)^,  is  formed 
(Group  XXIX.). 

4.  Benzene  nuclei  may  likewise  be  connected  through  two 
or  more  carbon  atoms,  as  in  Di-benzyl,  CgH^ — CHg — CHg — CgH^ 
(Group  XXX). 

5.  Lastly,  the  benzene  nuclei  may  be  so  grouped  together 
that  two  carbon  atoms  are  common  to  two  of  them,  as  in  anthra- 
cene and  naphthalene,  etc.  (Group  XXXI.  etc.). 

From  all  the  hydrocarbons  mentioned  under  the  above  para- 
graphs 1-4,  homologues  are  derived  ;  all  of  these  with  the 
exception  of  diphenyl  (which  possesses  the  benzene  character 
only)  have  like  toluene  partly  a  benzene  and  partly  a 


438 


XXVII.  DIPHENYL  GROUP. 


methane  character,  and  yield  completely  analogous  derivatives, 
like  the  benzene  hydrocarbons  in  the  narrower  sense  of  the 
term. 


XXVII.  DIPHENYL  GROUP. 

Summary. 


1.  Diphenyl,  C.YLr-C.H,,  =  C^^B.^,. 


29-Chloro-diphenyl  . 
0-,  p-Nitro-diphenyl 

Amido-diphenyl  .  , 


Diphenylol  . 


Cyano-diphenyl   .  . 
Diphenyl-carboxylic  acid 


C12H9CI 
CisHolOH) 


CisHglCOgH) 


p-^^-Dichloro-diphenyl 

'a  =  'p-p-YDinitYO- 
j3  =  o-p-j  diphenyl 

ip-p-)  =  Benzidine 
(  o-p-)  =  Diphenyline 


Carbazole 


Diphenols  .    .  . 

Diphenylene  oxide 

Dicyano-diphenyl 
Diphenyl-dicarboxylic  acid 


C12H8CI2 
C,2H8(NO,)2 


6:h:>nh 

Cj^HslOH), 
Ci2H8(CN)2 

Ci2ll8(C02H)2 


2.  Phenyl- tolyls,         C6H5--C6H4.  CH3. 

3.  Ditolyls,  C6H4(CH3)-C6H4(CH3), 

etc. 

4.  Diphenyl-benzene,  C6H4(C6H5)2. 

5.  Triphenyl-benzene,  C6H3(C6H5)3. 

Diphenyl,  C-^^^io  {P^^^Wi  1862).  When  bromo-benzene  in 
ethereal  solution  is  treated  with  sodium,  a  synthesis  of  diphenyl, 
analogous  to  the  Fittig  reaction  (p.  324),  is  effected : 


2C6H5Br  +  Nag 


C^H.-CeH^  +  2NaBr. 


Diphenyl  also  results  when  the  vapour  of  benzene  is  led 
through  a  red-hot  tube,  this  being  the  most  convenient  mode 
of  preparing  it.    It  is  contained  in  coal  tar.    Large  colourless 


DIPHENYL;  BENZIDINE. 


439 


plates,  readily  soluble  in  alcohol  and  ether;  M.  Pt.  71°,  B.  Pt. 
254°. 

Chromic  acid  oxidizes  diphenyl  to  benzoic  acid,  one  of  the  two 
benzene  nuclei  being  destroyed,  thus  leaving  only  one  carbon  atom 
joined  to  the  other  benzene  residue.  From  this  and  from  its  synthesis, 
the  constitutional  formula  of  diphenyl  follows  as  CgHg — CgHg. 


Derivatives. 

(See  Summary  ;  also  Schultz,  A.  207,  311). 

Like  benzene,  diphenyl  is  the  mother  substance  of  an 
extended  series  of  derivatives. 

Even  the  entrance  of  only  one  substituent  produces  isomers,  since 
the  latter  may  stand  either  in  the  o-,  m-,  or  ^-position  to  the  point  of 
junction  of  the  two  benzene  residues.  The  same  thing  applies  in  still 
greater  degree  to  isomeric  di-derivatives,  of  which  o-o-,  p-p-y  o-p-  etc. 
compounds  can  exist.  The  constitution  of  these  is  elucidated  either 
from  their  syntheses  or  from  their  products  of  oxidation ;  thus  a  chloro- 
diphenyl,  C12H9CI,  which  yields  p-chloro -benzoic  acid  when  oxidized  by 
chromic  acid,  is  obviously  p-chloro-diphenyl. 

The  substituents  take  up  the  ^-position  for  choice  ;  in  di-derivatives 
the  p-p'  (and  to  a  lesser  extent  the  o-p-)  position. 

C  H  NH 

Di-p-diamido  diphenyl,  benzidine^  CiQHg{NH2)2,  =  p^tt^  mtt^ 

(Zinin,  1845),  results  from  the  reduction  of  di-j?-dinitro- 
diphenyl  (the  direct  nitration  product  of  diphenyl);  also, 
together  with  diphenyline,  by  the  action  of  acids  upon 
hydrazo-benzene,  the  latter  undergoing  a  molecular  transfor- 
mation : 

CeHj-NH-NH-CeH,  =  NH^-CeH^-CgH -NH^ ; 

it  is  consequently  formed  directly  from  azo-benzene  by  treating 
it  with  tin  and  hydrochloric  acid. 

Benzidine  is  a  diatomic  base  which  crystallizes  in  colourless 
silky  plates,  readily  soluble  in  hot  water  and  alcohol  and 
capable  of  sublimation ;  M.  Pt.  1 22°.  It  is  characterized  by 
the  sparing  solubility  of  its  sulphate,  Cj2H^q(NH2)2.S04H2,  and 
by  various  colour  reactions.    Like  its  homologues  (tolidine, 


440 


XXVII.  DIPHENYL  GROUP. 


etc.),  it  is  of  special  importance  in  the  colour  industry,  since, 
by  coupling  its  diazo-compound  (tetrazo-diphenyl  chloride) 
with  naphthol  and  the  naphthylamine-sulphonic  acids,  etc., 
colours  are  produced  which  dye  unmordanted  cotton  directly, 
the  so-called     substantive "  or  cotton  dyes.    To  this  class 

belongs  the  dye  ConffO  C„H,-N=N-C,„H,(NH,)(S03Na) 
belongs  the  dye  Congo,  c,H -N=N-CioH,(NH2)(S03Na)' 

prepared  by  means  of  naphthionic  acid  (p.  465). 

(4) 

C6H4-NH2 

The  isomeric  Diphenyline,   |  (i)       (2)  ,  results  from  o-?9-dinitro- 
C6H4-NH2 

diphenyl,  and  also  as  a  bye-product  in  the  preparation  of  benzidine 
from  azo-benzene.    Needles,  M.  Pt.  45°.    Its  sulphate  is  readily  soluble. 
C  H 

Carbazole,  C12H9N,  =    -^^^NH,  the  imide  of  diphenyl,  is  con- 

tained  in  coal  tar  and  in  crude  anthracene.  It  is  formed  e.g,  by  passing 
the  vapour  of  diphenylamine  or  of  aniline  through  red-hot  tubes,  just 
as  diphenyl  is  obtained  from  benzene  : 

(C6H5),NH  =  (CeHJ^NH  +  H^. 

It  crystallizes  in  colourless  plates  sparingly  soluble  in  cold  alcohol, 
M.  Pt.  238°.  It  distils  unchanged  and  is  characterized  by  its  great 
capability  of  sublimation.  Concentrated  sulphuric  acid  dissolves  it  to 
a  yellow  solution,  and  it  forms  an  acetyl-  and  a  nitro-compound,  etc. 
The  nitrogen  in  it  very  probably  occupies  the  di-ortho-position,  which 
would  make  it  a  pyrrol  derivative  (see  indole). 

The  Dioxy-diphenyls,  Ci2H8(OH)2,  of  which  four  isomeric  modifica- 
tions are  known,  result  partly  by  diazotizing  benzidine,  partly  by  fusing 
diphenyl-disulphonic  acid  with  potash,  and  partly  by  fusing  phenol 
with  potash  ;  in  the  last  case  hydrogen  is  separated  and  two  benzene 
residues  join  together. 

C  H 

Diphenylene  oxide,  %^^^0,  is  obtained  by  distilling  phenol  with 

oxide  of  lead  ;  it  crystallizes  in  plates  which  distil  without  decomposi- 
tion. 

Hexoxy-diphenyl,  Ci2H4(OH)6  (silvery  glancing  plates),  which  dis- 
solves in  potash  with  a  beautiful  violet-blue  colour,  is  the  mother  sub- 
stance of  Coerulignone  or  Cedriret,  CieHigOg,  a  violet-coloured  compound 
which  is  formed  when  crude  pyroligneous  acid  is  purified  with  chromate 
of  potash,  and  also  from  the  oxidation  of  the  dimethyl-pyrogallol  of 
beech-wood  tar  by  means  e.g.  of  potassic  ferricyanide;  in  the  latter  case 
there  is  not  only  a  joining  together  of  the  two  benzene  nuclei,  but  also 


COERULiaNONE  ;  DIPHENIC  ACID.  441 

a  separation  of  hydrogen,  with  the  production  of  a  linking  of  somewhat 
the  same  nature  as  in  superoxides  : 

Coerulignone  crystallizes  in  fine  steel-grey  needles  soluble  in  con- 
centrated sulphuric  acid  with  a  blue  colour.  Tin  and  hydrochloric 
acid  convert  it  into  Hydro -coerulignone,  =  tetramethyl-hexoxy-diphenyl, 
which  is  split  up  into  methyl  chloride  and  hexoxy-diphenyl  on  warming 
with  concentrated  hydrochloric  acid  {Liehermann). 

The  carboxylic  acids  of  diphenyl  are  obtained  from  the  correspond- 
ing cyanides,  which  on  their  part  are  prepared  by  distilling  the 
sulphonic  acids  of  diphenyl  with  KCN.  Di-^^-diphenyl-dicarboxylic  acid, 
C22H8(C02H)2,  a  white  powder  insoluble  in  water,  alcohol  and  ether,  is 
an  oxidation  product  of  phenanthrene  and  similar  compounds ;  Diphenic 
C  H  CO  H 

acid,  A^TT^Virk^TTj  ^  di-ortho-compound,  crystallizes  in  needles  or  plates 

06x14.  CO2H 

which  are  readily  soluble  in  the  solvents  just  mentioned ;  M.  Pt.  229°. 
Both  of  these  are  dibasic  acids,  which  yield  diphenyl  when  heated  with 
soda-lime. 

The  homologues  of  diphenyl  are,  like  the  latter,  obtained  by 
means  of  the  Fittig  reaction.  Analogous  to  benzidine  is  o-Tolidine, 
012116(0113)2(^112)2,  M.  Pt.  128°,  which  is  likewise  used  in  the  manufac- 
ture of  cotton  dyes,  e.g.  Azo-blue  and  Benzo-purpurin.  It  is  combined 
in  the  former  with  naphthol-sulphonic,  and  in  the  latter  with  naph- 
thionic  acid. 


Appendix.  By  the  action  of  sodium  upon  a  mixture  of  ^-dibromo- 
benzene  and  bromo-benzene,  there  is  formed  Diphenyl-benzene, 
05114(06115)2  (flat  prisms,  M.  Pt.  205°),  which  is  oxidizable  to  diphenyl- 
monocarboxylic  and  terephthalic  acids. 

When  hydrochloric  acid  gas  is  led  into  acetophenone,  O^Hg.OO.OHg, 
a  reaction  analogous  to  the  formation  of  mesitylene  from  acetone 
ensues,  and  there  is  produced  Triphenyl-benzene,  06H3(06Hg)3  (1  :  3  :  5  ; 
rhombic  plates). 


442  XXVIII.  DIPHENYL-METHANE  GROUP. 

XXVIII.  DIPHENYL-METHANE  GROUP. 


Summary, 


(^'6^5)2=^112 
Diphenyl-methane. 

(96^5)2=CH-CH3 

Diphenyl-ethane. 
Diphenyl-acetic  acid. 

Phenyl-tolyl-methanes. 

CfiH5-CH2-C6H4-C02H 
Benzyl-benzoic  acids, 
etc. 

(C6H5),=CH.OH 
Benzhydrol. 

in  XT  X  -(VC\Tf\_cn  "FT 
Benzylic  acid. ' 

C6H5-CH(OH)-C6H4-CH3 
Phenyl-tolyl  carbinols. 

C6H5-CH(OH)-C6H4-C02H 
Benzhydril-benzoic  acids. 

(C6H,),=C0 
Benzophenone. 

CgIl5-CO-CgH4-CH3 
Phenyl-tolyl  ketones. 

C6H5-CO-C6H4-CO2H 
Benzoyl-benzoic  acids. 

Fluorene. 

9;JJ;>cH.oH 

Fluorenyl  alcohol. 

Diphenylene  ketone. 

Diphenyl-methane  is  derived  from  methane  by  the  substitu- 
tion of  two  hydrogen  atoms  by  two  phenyl-groups,  just  as 
toluene  is  by  the  substitution  of  one.  It  consequently 
resembles  the  latter  hydrocarbon  in  most  of  its  relations, 
with  this  important  difference  that,  as  it  no  longer  contains 
a  CHg-group,  it  cannot  yield  an  acid  containing  an  equal 
number  of  carbon  atoms  in  the  molecule  upon  oxidation ; 
combination  with  oxygen  produces  benzhydrol  and  benzo- 
phenone. As  soon,  however,  as  more  carbon  atoms  are  made 
to  enter  the  molecule,  the  same  conditions  repeat  themselves 
as  in  the  case  of  toluene,  xylene,  etc.,  and  the  most  various 
acids,  alcohol-acids,  ketone-acids,  etc.  can  be  obtained  from 
the  resulting  homologues. 

Formation  of  diphenyl-methane  and  its  derivatives. 

1.  Diphenyl-methane  is  produced  by  the  action  of  benzyl 


MODES  OF  FORMATION.  443 

chloride  upon  benzene,  in  presence  of  zinc  dust  (Zincke,  A.  159, 
374),  or  of  aluminium  chloride  (Friedel  and  Crafts)  : 

CeH-CH^Cl  +  C„He  =  C,H -CH^-CeH^  +  HCl. 

The  homologues  of  benzene,  and  also  the  phenols  and  tertiary  amines, 
may  be  used  here  instead  of  benzene  itself. 

In  an  exactly  analogous  manner  diphenyl-methane  results  from  the 
action  of  methylene  chloride,  CH2CI2,  upon  benzene  in  presence  of 
chloride  of  aluminium : 

CH2CI2  +  2C6H,  =  CH^lCeHg)^  +  2HC1. 

2.  Diphenyl-methane  hydrocarbons  are  formed  by  the  action 
of  the  fatty  aldehydes,  e.g.  acetic  or  formic  aldehyde,  upon 
benzene,  etc.  in  the  presence  of  concentrated  sulphuric  acid 
(Baeyer,  B.  6,  221) : 

CH3— CHO  +  2C,He  =  CH3— CH(C6H5)2  +  H^O. 

V   y 

Y 

Diphenyl-ethane. 

The  acetic  and  formic  aldehydes  are  employed  here  in  the  form  of 
para-aldehyde  and  methylal.  When  aromatic  aldehydes  are  used, 
triphenyl-methane  derivatives  result  (p.  446). 

2\  Aromatic  alcohols  react  with  benzene  and  sulphuric  acid  in  an 
analogous  manner  ( V.  Meyer) ; 

C6H5-CH2.OH  +  CeH^  =  CeHg-CH^-CeHs  +  H^O. 

Similar  reactions  have  also  been  brought  about  by  means  of  ketones, 
aldehyde-acids  and  ketone-acids  on  the  one  hand,  and  phenol  and 
tertiary  anilines  on  the  other. 

3.  Benzophenone  is  produced  by  the  action  of  benzoic  acid 
upon  benzene  in  presence  of  P2^5  (^^^-^j  B.  6,  536) : 

C,H,-CO.OH  +  G,U,  ==  CeH^-CO-C.H,  +  H^O. 

4.  Benzophenone  and  the  analogous  ketones  result  upon 
heating  the  mixed  calcium  salts  of  the  aromatic  acids,  accord- 
ing to  the  general  mode  of  formation  2  of  the  ketones ;  thus 
calcium  benzoate  heated  alone  yields  benzophenone : 

CgHg.COgCa  +  CeH5.C02ca  =  C^jH^.CO.CgHg  +  CaCOg. 

Mixed  ketones  (p.  139)  can  be  prepared  in  the  same  way. 

5.  Ketones  are  likewise  produced  by  the  action  of  benzoyl- 


444 


XXVIII.  DIPHENYL-METHANE  GROUP. 


chloride,  CgH^CO.Cl,  etc.  upon  benzene,  etc.  in  presence  ol 
AlgClg  (Friedel  and  Crafts;  also  Ador,  B.  10,  1854) : 

C,H,.C0.C1  +  C,H,  =  G,Yl,.GO.C,R,  +  HCl. 

In  this  case  also,  as  in  method  3,  phenols  (or,  better,  phenolic  ethers) 
or  tertiary  amines  may  be  employed  in  place  of  the  benzene  hydro- 
carbons. 

5*.  Since  the  acid  chlorides  are  formed  from  the  benzenes  with 
cobalt  chloride  and  zinc  chloride,  these  reagents  may  be  used  directly 
for  the  production  of  ketones,  under  suitable  conditions. 

The  above  ketones  are,  like  all  others,  converted  into  their  cor- 
responding hydrocarbons  by  distilling  over  zinc  dust,  or  by  heating 
with  hydriodic  acid  and  phosphorus,  etc.  (cf.  p.  38). 

1.  Diphenyl-methane,  {G(^fl^)2GB.^,  is  most  conveniently 
prepared  from  benzyl  chloride,  benzene  and  AlgCl^.  It 
crystallizes  in  colourless  needles  of  very  low  melting  point 
(26°),  is  readily  soluble  in  alcohol  and  ether,  has  a  pleasant 
odour  of  oranges,  and  distils  unaltered;  B.  Pt.  272°. 

It  yields  nitro-,  amido-  and  oxy-derivatives.  By  the  action  of 
bromine,  aided  by  warming,  Diphenyl-bromo -methane,  (C6H5)2CHBr,  is 
obtained,  and  when  this  latter  is  heated  with  water  to  150°,  it  goes  into : 

Benzhydrol,  diphenyl-carbinol,  (C6H5)2CH.OH,  which  also  results 
from  benzophenone  and  sodium  amalgam.  It  crystallizes  in  glancing 
silky  needles,  possesses  in  every  respect  the  character  of  a  secondary 
alcohol  (forming  compound  ethers,  amines,  etc.),  and  is  readily  oxidiz- 
able  into  the  corresponding  ketone. 

Benzophenone,  diphenyl-ketone,  {GqH.^)^GO.  This  compound 
is  prepared  by  distilling  benzoate  of  lime  (Feligot,  1834),  and 
also  results  directly  from  the  oxidation  of  diphenyl-methane 
with  chromic  acid.  It  is  the  simplest  pure  aromatic  ketone, 
and  possesses  the  ketonic  character  in  its  entirety,  being 
reducible  to  benzhydrol,  yielding  with  PCI5  a  dichloride, 
(CgH5)2C=Cl2,  and  combining  with  phenyl-hydrazine,  etc. 

It  is  characterized  by  being  dimorphous,  crystallizing  in  large 
rhombic  prisms,  M.  Pt.  49°  (stable),  and  also  in  rhombohedra,  M. 
Pt.  27°  (unstable)  ;  B.  Pt.  297°.  Fused  potash  decomposes  it  into 
benzoic  acid  and  benzene,  while  red-hot  zinc  dust  regenerates  diphenyl- 
methane. 

Among  its  derivatives  may  be  mentioned  Di-jp-diamido-benzophenone, 
CO(C6H4.NH2)2,  whose  tetra-methyl  compound,  Tetramethyl-diamido- 


BENZILIC  ACID;  BENZOYL-BENZOIC  ACIDS.  445 


benzophenone,  CO[C6H4Nr(CH3)2]2,  results  from  the  action  of  COCI2 
upon  dimethyl-aniline  : 

COCI2  +  2C6H5.N(CH3)2  =  CO[C6H4N(CH3)2]2  +  HCl. 

It  is  nearly  related  to  certain  dyes,  being  converted  into  methyl 
violet  (p.  452)  upon  further  treatment  with  dimethyl-aniline,  and  into 
Auramine  or  its  derivatives  (beautiful  yellow  dyes)  by  ammonia  or 
amine  bases  respectively. 

The  ^-position  of  the  amido-groups  has  been  proved. 

jo-Dioxy-benzophenone,  [C6H4(OH)2]CO,  results  among  other  methods 
from  the  decomposition  of  complicated  benzene  dyes,  such  as  rosaniline 
and  aurin,  by  heating  these  with  water  or  with  alkalies.  It  can  be 
prepared  synthetically  from  anisaldehyde  (B.  14,  328),  and  therefore 
contains  the  hydroxy  Is  in  the  _p-position. 


Homologues  of  Diphenyl-methane ;  Fluorene, 

2.  Diphenyl- ethane,  (C6Hg)2CH — CH3  (unsymmetrical,  see  p.  457)> 
is  obtained  from  benzene  and  para-aldehyde  as  given  on  p.  443.  It  is  a 
liquid  which  boils  without  decomposition  and  which  is  oxidized  to 
benzophenone  by  chromic  acid.    From  it  is  derived : 

Benzilic  acid,  diphenyl-glycollic  acid,  (C6H5)2=C(OH)— COgH,  which 
results  by  a  molecular  transformation  upon  fusing  benzile  (p.  458)  with 
potash.  It  crystallizes  in  needles  or  prisms,  soluble  in  H2SO4  with  a 
blood-red  colour,  and  is  reduced  by  hydriodic  acid  to  : 

Diphenyl-acetic  acid,  (C6Hg)2=CH — COgH  (needles  or  plates),  which 
on  its  part  is  obtained  synthetically  from  phenyl-bromacetic  acid, 
CgHg — CHBr — CO2H,  benzene  and  zinc  dust,  according  to  mode  of 
formation  1,  p.  442;  this  yields  proof  of  its  constitution.  Both  sub- 
stances yield  benzophenone  upon  oxidation ;  here,  therefore,  as  in  the 
simpler  cases,  all  the  carbon  is  separated  which  is  not  directly  linked 
to  the  benzene  nuclei. 

3.  Phenyl-tolyl-methanes,  CgHg— CHg— C6H4— CH3.    The  p-  and  o- 

compounds  are  obtained  from  benzyl  chloride  and  toluene,  as  given  at 
p.  443.  They  yield  on  oxidation  the  corresponding  Phenyl-tolyl- 
ketones,  CgHg — CO — C6H4 — CH3,  and  finally  the  Benzoyl-benzoic  acids, 
CgHs— CO— C6H4— CO2H  (B.  6,  907).  Of  these,  the  o-acid,  for 
example  (M.  Pt.  127°),  has  also  been  prepared  synthetically  by  heating 
phthalic  anhydride  with  benzene  and  Al2Clg.  They  are  reducible  to 
benzhydril-benzoic  acids  (or  anhydrides)  and  benzyl-benzoic  acids 
respectively.  When  the  o-acid  is  heated  with  P2O5  to  180°,  it  yields 
anthraquinone,  various  transformations  into  the  anthracene  scries 
having  been  effected  from  o-phenyl-tolyl-methane  and  -ketone. 


446 


XXIX.  TRIPHENYL-METHANE  GROUP. 


4.  Ditolyl-methane,  (CH3.C6H4)2CH2. 

C  H 

5.  Fluorene,  diphenylene-methane,  -^^^CHg,  stands  in  the  same 

relation  to  diphenyl-methane  as  carbazole  (p.  440)  does  to  diphenyl- 
amine;  it  is  at  the  same  time  a  diphenyl  and  a  methane  derivative.  It 
is  contained  in  coal  tar  and  crystallizes  in  colourless  plates  with  a  violet 
fluorescence;  M.  Pt.  113°,  B.  Pt.  295°.  The  corresponding  ketone, 
Diphenylene  ketone,  CioHg^CO  (yellow  prisms,  M.  Pt.  84°),  is  obtained 
e.g.  by  heating  phenanthrene  quinone  with  lime,  and  is  converted  into 
fluorenyl  alcohol  by  nascent  hydrogen  and  into  diphenyl-carboxylic 
acid,  CgHg — C6H4 — COgH,  by  fusion  with  potash. 


XXIX.  TRIPHENYL-METHANE  GROUP. 

Triphenyl-methane,  CH(CgH5)3,  results  from  the  entrance  of 
three  phenyl  groups  into  the  methane  molecule;  among  its 

homologues  are  e.g.  Diphenyl-tolyl-methane,  CH^^  |j  ^^jj  , 

Phenyl-ditolyl-methane,  CH-<^^p^»§^^pTT  \  ,  etc. 

These  hydrocarbons  are  of  especial  interest  as  being  the 
mother  substances  of  an  extensive  series  of  dyes. 

Their  formation  is  effected  in  a  manner  analogous  to  that  of 
the  diphenyl-methane  derivatives,  i.e.  by  the  aid  of  zinc  dust 
or  aluminium  chloride  when  chlorine  compounds  are  used,  or 
by  the  aid  of  phosphoric  anhydride  when  oxygen  compounds 
are  employed. 

Thus,  triphenyl-methane  results : 

1.  From  benzal  chloride  and  benzene  : 

C6H5.CHCI2  +  2C6H6  =  CH(C6H5)3  +  3HC1 ; 
1*.  from  benzaldehyde,  benzene  and  zinc  chloride  (see  p.  339) ; 

2.  from  chloroform  and  benzene  by  means  of  AlgClg  : 

SCcHg  +  CHCI3  =  CH(C6H5)3  +  3HC1 ; 

3.  from  benzhydrol  and  benzene  : 

(C6H,),=CH.0H  +  CeH,  =  {C,U,),=Q11.(0,^,)  +  H,0. 
The  leuco-base  of  bitter-almond-oil  green  (cf  p.  448)  results 
from  benzaldehyde  and  dimethyl  aniline. 


TRIPHENYIrMETHANE. 


447 


By  using  other  amine  bases  and  also  phenols,  a  series  of  allied  com- 
pounds (which  are  often  dyes)  is  obtained,  the  separation  of  water  being 
facilitated  by  the  addition  of  zinc  chloride,  concentrated  sulphuric 
acid,  or  anhydrous  oxalic  acid. 


1.  Triphenyl-methane,  CigH^g,  =  CH(C6H5)3  {KekuU  and 
Franchimont,  B.  5,  906).  This  compound  may  be  prepared 
from  chloroform  and  benzene  by  the  Friedel-Crafts  reaction 
(cf.  A.  194,  152),  diphenyl-methane  being  produced  at  the 
same  time;  also  by  diazotizing  jp-leucaniline,  C^9H;l3(NH2)3,  i.e. 
by  eliminating  the  amido-groups  from  it.  It  crystallizes  in 
beautiful  white  prisms,  insoluble  in  water  and  only  slightly 
soluble  in  cold  alcohol,  but  readily  soluble  in  hot  alcohol, 
ether  and  benzene;  M.  Pt.  93°,  B.  Pt.  359°. 

It  crystallizes  from  benzene  with  one  molecule  of  "  benzene  of 
crystallization,"  which  is  also  the  case  with  many  triphenyl-methane 
derivatives.  When  triphenyl-methane  is  treated  with  bromine  in  a 
solution  of  .carbon  bisulphide,  the  methane  hydrogen  atom  is  exchanged 
for  bromine  with  the  formation  of  : 

Triphenyl-methane  bromide,  (06115)3.  CBr,  which,  when  boiled  with 
water,  goes  into  : 

Triphenyl-carbinol,  (CgH5)3C.(OH).  This  crystallizes  in 
glancing  prisms,  M.  Pt.  157°,  and  can  be  sublimed  unchanged; 
it  may  also  be  prepared  directly  by  oxidizing  a  solution  of 
triphenyl-methane  in  glacial  acetic  acid  with  chromic  acid. 

Fuming  nitric  acid  acts  upon  triphenyl-methane  to  form  Trinitro- 
triphenyl-methane,  (C6H4.N02)3.CH  (yellow  scales),  which  is  in  its 
turn  converted  into  : 

Trinitro-triphenyl-carbinol,  (C6H4.N02)3C(OH),  by  chromic  acid. 
The  latter  gives  para-rosaniline,  (C6H4.NH2)3C.OH,  when  treated  with 
zinc  dust  and  glacial  acetic  acid,  and  the  former,  para-leucaniline 
(p.  450). 

Homologous  with  triphenyl-methane  are  the  : 

2.  Diphenyl-tolyl-methanes,  {G^'H,)^=CB.—G,'H,{m,), 
From  these  also  dyes  are  derived,  especially  from  Diphenyl- 
m-tolyl-methane  (in  which  the  CH3  occupies  the  mcta-position 
with  regard  to  the  methane  carbon  atom),  which  can  be  pre- 


448  XXIX.  TRIPHEN^METHANE  GROUP. 

pared  by  diazotizing  ordinary  leucanilinej  it  crystallizes  in 
small  prisms,  M.  Pt.  59-5°. 

Triphenyl-methane  Dyes. 

Of  the  derivatives  of  triphenyl-methane  and  of  diphenyl- 
tolyl-methane,  those  are  especially  interesting  which  result 
from  them  by  the  entrance  of  amidogen  or  hydroxyl  (or  also 
carboxyl).  The  entrance  of  three  amido-  or  hydroxyl-groups 
converts  them  into  the  leuco-compounds  of  dyes,  some  of 
which  latter  are  of  great  value.  Two  amido-groups  suffice  for 
the  full  development  of  the  dye  character  only  when  the 
amido-hydrogen  atoms  are  replaced  by  alcoholic  radicles. 

We  distinguish  between  the  following  groups  : 

1.  that  of  diamido-triphenyl-methane  (the  bitter-almond-oil 
green  group) ; 

2.  that  of  triamido-triphenyl-methane  (the  rosaniline 
group) ; 

3.  that  of  trioxy-triphenyl-methane  (the  aurin  group) ; 

4.  that  of  triphenyl-methane-carboxylic  acid  (the  eosin 
group). 

Leuco-bases  or  Leuco-compounds  of  dyes  are  compounds 
which  result  from  the  reduction  of  the  dyes  themselves  (in 
most  cases  by  the  addition  of  two  atoms  of  hydrogen) ;  they 
are  colourless,  but  are  converted  into  the  dyes  by  oxidation. 

All  the  dyes  of  the  triphenyl-methane  group,  and  also 
indigo,  methylene  blue,  safranine,  etc.  are  capable  of  yielding 
such  leuco-compounds  (mostly  by  the  action  of  zinc  and  hydro- 
chloric acid,  stannous  chloride,  or  ammonium  sulphide). 

The  oxidation  of  the  leuco-compounds  is  often  quickly  effected  by 
the  oxygen  of  the  air  (e.g.  in  the  cases  of  indigo  white  and  of  leuco- 
methylene  blue) ;  in  the  triphenyl-methane  group  it  is  slower  and 
frequently  more  complicated.  Leuco-bitter-almond-oil  green  readily 
goes  into  the  corresponding  colour-base  when  treated  with  PbOg  in  acid 
solution,  and  leucaniline  does  the  same  when  warmed  with  chloranil  in 
alcoholic  solution,  or  when  its  hydrochloride  is  heated  either  alone  or 
with  a  concentrated  solution  of  arsenic  acid,  or  with  metallic  hydroxides 
such  as  Fe2(0H)g. 


BITTER-ALMOND-OIL  GREEN,  ETC. 


449 


1,  Diamido-triphenyl-methane  Group. 

Diamido-triphenyl-methane,  CgHg — CH(C6H4.NH2)2,  is  prepared  by 
the  action  of  zinc  chloride  or  of  fuming  hydrochloric  acid  upon  a 
mixture  of  benzaldehyde  and  aniline  sulphate  or  chloride  : 

CeHs.CHO  +  2C6H5NH2  =  C6H5.CH=(C6H4.NH2)2  +  H^O. 

It  crystallizes  in  glancing  prisms.  The  colourless  salts  yield  an 
unstable  blue-violet  dye,  Benzal  violet,  upon  oxidation.  Methylation 
converts  the  base  into  : 

Tetramethyl-di-p-amido-triphenyl-methane,  leuco -malachite  green, 
CeHg — CH=[C6H4.N(CH3)2]25  which  is  prepared  on  the  technical  scale 
by  heating  benzaldehyde  and  dimethyl-aniline  with  zinc  chloride  or 
anhydrous  oxalic  acid  (p.  399  ;  0.  Fischer^  A.  206,  103).  It  forms 
colourless  plates  or  prisms.  As  a  diatomic  base  it  yields  colourless 
salts,  and  is  slowly  converted  by  the  air,  but  immediately  by  other 
oxidizing  agents,  such  as  Pb02  +  H2SO4,  into  (the  salts  of) : 

Tetramethyl-diamido-triphenyl-carbinol, 

C6H5.C(OH)— [C6H4N(CH3)2]2.  The  free  base  is  obtained  by 
precipitating  the  salts  with  alkali.  It  crystallizes  in  colourless 
needles  and  dissolves  in  cold  acid  to  a  colourless  solution; 
upon  warming,  however,  the  intensive  green  colouration  of 
the  salts  is  produced.  (For  an  explanation  of  this,  see  p. 
451). 

The  double  salt  with  zinc  chloride  or  the  oxalate  of  this 
base  is  the  valuable  dye  Bitter-almond-oil  green,  malachite 
green  or  Victoria  green,  which  forms  green  plates,  readily 
soluble  in  water.  This  can  also  be  prepared  directly  by  heat- 
ing benzo-trichloride  with  dimethyl-aniline  and  chloride  of  zinc 
{Doebner). 

Brilliant  green  is  the  corresponding  ethyl  compound. 

If,  instead  of  benzaldehyde,  o-,  m-  or  ^^-nitro-benzaldehyde  is  used, 
nitro-derivatives  of  (leuco-)  malachite  green  are  obtained. 

The  analogous  ^^-Nitro- diamido-triphenyl-methane, 
C6H4(N02)-CH(C6H4.NH2)  2,  can  be  prepared  from  p-nitro-benzalde- 
hyde,  aniline  sulphate  and  sulphuric  acid.  It  goes  into  para-leucaniline 
upon  reduction.  The  reduction  of  the  isomeric  m-  and  o-compounds 
yields  isomers  of  leucaniline  (Pseudo-  and  Ortho-leucanilines),  which  give 
violet  and  brown  dyes  upon  oxidation. 


(506) 


2F 


450 


XXIX.  TRIPHENYL-METHANE  GROUP. 


2.  Rosaniline  Group. 

Fuchsine  was  first  obtained  in  1856  by  Natanson  [who  noticed  the 
formation  of  a  red  substance,  in  addition  to  that  of  aniline  hydrochloride 
and  ethylene-aniline,  when  ethylene  chloride  was  allowed  to  act  upon 
aniline  at  a  temperature  of  200°  (A.  98,  297)],  and  shortly  afterwards 
by  ^.  W.  Hofmann  (by  the  action  of  carbon  tetrachloride  upon  aniline), 
and  was  first  prepared  on  the  technical  scale  in  1859.  Hofmann' s 
scientific  researches  on  this  subject  date  from  1861.  The  chemical 
constitution  was  made  clear  by  Emil  and  Otto  Fischer  in  1878  (A.  194, 
172).    (Cf.  also  Garo  and  Grcehe,  B.  11,  1117.) 

The  rosaniline  dyes  are  derived  partly  from  triphenyl- 
methane  and  partly  from  diphenyl-m-tolyl-methane ;  in  the 
former  case  they  are  often  designated  para-cofnpounds  {e,g, 
*'para-rosaniline,"  because  it  is  prepared  from  aniline  and 
para-toluidine ;  "  para-rosolic  acid  "). 

Para-leucaniline,  CigH^gNg,  and  Leucaniline,  C20H21N3, 
result  from  the  reduction  of  the  corresponding  trinitro- 
compounds  and  also  of  the  corresponding  dyes,  para-rosaniline 
and  fuchsine  j  the  first  named  likewise  from  the  reduction  of 
p-nitro-diamido-triphenyl-methane.  The  free  leuco-bases  are 
thrown  down  by  ammonia  from  solutions  of  their  salts  as 
white  or  reddish  flocculent  precipitates,  and  crystallize  in 
colourless  needles  or  plates;  they  melt  at  148°  and  100° 
respectively.  As  triatomic  bases  they  form  colourless  crystal- 
line salts. 

Para-rosaniline,  C^gH^gNgO,  and  Rosaniline,  CgoHgiNgO, 
are  the  bases  of  the  fuchsine  dyes.  They  are  obtained  by 
precipitating  solutions  of  their  salts  with  alkalies,  and  crystallize 
from  hot  water  or  alcohol  in  colourless  needles  or  plates.  Both 
are  triatomic  bases,  stronger  than  ammonia. 

They  yield  tri-diazo-compounds  with  nitrous  acid,  compounds  which 
go  into  the  corresponding  phenol  dyes  (aurin  and  rosolic  acid)  when 
boiled  with  water  ;  they  are  therefore  primary. 

Constitution.  The  relations  between  the  rosanilines  and  triphenyl- 
methane  have  been  made  clear  by  the  transformation  of  leucaniline 
(by  diazotizing  it)  into  diphenyl-tolyl-methane,  and  the  analogous  con- 
version of  para-leucaniline  into  triphenyl-methane  {E.  and  0.  Fischer ^ 
loc.  cit.). 

Para-leucaniline  is  thus  triamido-triphenyl-methane,  while  leucaniline 


PARA-ROSANILINE  AND  ROSANILINE. 


451 


is  triamido-diphenyl-tolyl-methane.  The  dye-bases  belonging  to  them 
are  the  corresponding  carbinols,  e.g.  rosaniline  is  triamido-diphenyl- 
tolyl-carbinol.  The  three  amido-groups  can  be  introduced  synthetically, 
as  given  at  p.  448.  They  are  distributed  equally  among  the  three 
benzene  nuclei,  as  is  clear  from  the  synthesis  of  para-leucaniline  by 
means  of  p-nitro-benzaldehyde  (p.  449).  We  have  therefore  e.g.  the 
following  formulae  :  , 

/C6H4.NH2  /C6H4.NH2 

\C6H4.NH2  \C6H3(CH3).NH2. 
Para-leucaniline.  Kosaniline. 

The  para-position  of  the  NHg-groups  with  regard  to  the  methane 
carbon  atom  is  proved  as  follows  :  (1)  Para-rosaniline  yields  p-dioxy- 
benzophenone  (p.  445;  B.  11,  1434)  when  heated  with  water,  while 
rosaniline  gives  p-diamido-methyl-benzophenone  (B.  16,  1928 ;  19, 
107).  (2)  Diamido-triphenyl-methane  (from  benzaldehyde  and  aniline) 
is  a  di-p- compound,  because  it  is  likewise  convertible  into  di-p-oxy- 
benzophenone  (B.  12,  1466).  Para-leucaniline  (from  ^^-nitro-benzalde- 
hyde  and  aniline,  B.  15,  101)  is  therefore  a  tri -^-compound. 

The  salts  of  rosaniline  and  para-rosaniline,  Fuchsine,  C20H20N3CI, 
Rosaniline  nitrate,  C2oH2oN3(N03),  Rosaniline  acetate,  €201120^3(^^211302), 
etc.  are  the  actual  dyes.  While  they  possess  a  magnificent  fuchsine-red 
colour  in  solution,  and  have  intense  colouring  power  (dyeing  wool  and 
silk  without  a  mordant),  their  crystals  are  of  a  brilliant  metallic  green 
with  cantharides  glance,  i.e.  of  nearly  the  complementary  colour.  They 
are  fairly  soluble  in  hot  water  and  alcohol. 

In  the  formation  of  the  salts  water  is  separated,  a  peculiar  nitrogen- 
carbon  linking  being  manifestly  brought  about,  thus  : 

/C6H4.NH2 

C(OH)(C6H4.NH2)3  +  HCl  =  C^C6H4.NH2        +  H.O. 

I  \C6H4.NH,  HCl 

An  analogous  separation  of  water  is  also  observed  in  the  formation 
of  salts  of  the  malachite  green  base,  but  this  only  takes  place  upon 
warming,  as  is  proved  by  the  fact  that  it  dissolves  without  colour  in 
cold  acids,  and  that  the  intense  colouration  of  the  salts  first  becomes 
apparent  after  warming  the  solution. 

In  addition  to  the  above  salts  there  also  exist  acid  ones,  e.g. 
C20H20N3CI  +  2HC1  (which  yields  a  yellow-brown  solution,  not  a 
fuchsine-coloured  one)  ;  these  dissociate  into  the  neutral  salts  and  free 
acid  upon  the  addition  of  much  water. 

In  the  manufacture  of  fuchsine  either  a  mixture  of  aniline 
with  0-  and  ^-toluidine  is  oxidized  by  syrupy  arsenic  acid,  or 
a  mixture  of  nitro-benzene  with  aniline  and  toluidine  is 


452 


XXIX.  TRIPHENYL-METHANE  GROUP. 


heated  with  iron  filings  and  hydrochloric  acid  (Courier).  For 
the  preparation  of  the  higher  homologues,  o-  and  ^-nitro- 
toluenes  may  be  employed  instead  of  nitro-benzene. 

Instead  of  arsenic  acid,  stannic  chloride  or  mercuric  chloride  or 
nitrate,  etc.  may  be  used  for  the  oxidation.  If  o-toluidine  is  present 
in  the  mixture  to  be  oxidized,  rosaniline  is  formed,  and  if  it  is  absent, 
para-rosaniline.  When  pure  aniline  is  oxidized  alone,  it  yields  no 
fuchsine  at  all,  but  products  of  the  nature  of  indulin.  This  is  ex- 
plained by  the  fact  that  for  the  formation  of  fuchsine  a  carbon  atom 
is  required  which  shall  serve  to  link  the  benzene  nuclei  together,  a 
so-called  ^*  methane-carbon " ;  in  the  action  of  carbon  tetrachloride 
upon  aniline,  this  carbon  originates  from  the  tetrachloride,  and  in  the 
oxidation  of  a  mixture  of  aniline  and  toluidine,  from  the  methyl  group 
of  the  latter,  as  is  shown  in  the  following  equation  : 

H3C  +  C6H5.NH2  -  3fT2    =  C^CeH^.NH^. 
+  CgHg.NH^  I  \C6H4.NH 

When  rosaniline  is  heated  with  hydrochloric  or  hydriodic 
acid  to  200°,  it  is  split  up  into  aniline  and  toluidine ;  when 
superheated  with  water,  para-rosaniline  yields  j9-dioxy-benzo- 
phenone,  ammonia  and  phenol.  A  solution  of  fuchsine  is 
decolourized  by  sulphurous  acid,  an  addition  product,  fuchsine- 
sulphurous  acid,  being  formed.  This  solution  is  a  delicate 
reagent  for  aldehydes,  which  colour  it  violet-red  (see  p.  135.) 

For  the  homologues  and  isomers  of  rosaniline,  see  B.  15,  1453. 

Derivatives  of  Rosaniline. 

1.  Methylated  rosanilines  (Hofmann,  Lauth). 

The  red  colour  of  para-rosaniline  and  of  rosaniline  is  changed 
into  violet  by  the  entrance  of  methyl  or  ethyl,  the  intensity 
of  the  latter  colour  increasing  with  an  increasing  number  of 
these  groups.  The  salts  of  Hexamethyl-para-rosaniline  have 
a  magnificent  bluish-violet  shade.  In  the  manufacture  of 
these  "Methyl-violets"  one  may  either  (1)  methylate  rosaniline 
(by  means  of  CH^Cl  or  CH3I);  or  (2)  oxidize,  instead  of 
aniline,  a  methylated  aniline  such  as  dimethyl-aniline  (e.g.  by 
means  of  cupric  salts),  whereby  para-rosaniline  derivatives 
result ;  or,  (3)  allow  phosgene  to  act  upon  dimethyl-aniline  (or 


DERIVATIVES  OF  ROSANILINE. 


453 


the  latter  to  act  upon  the  tetramethyl-diamido-benzophenone 
at  first  produced)  (cf.  B.  17,  Eef.  339) : 

COCI2  +  3C6H5.N(CH3)2  =  C(OH)[CeH4.N(CH3)2]3  +  2HC1. 

In  the  last  case  hexamethyl-violet,  termed  "  Crystal  violet " 
on  account  of  the  beauty  of  its  crystals,  results,  while  the 
methyl-violets  prepared  by  other  methods  are  mixtures  of 
hexa-,  penta-  and  tetra-methyl-rosanilines  and  are  amorphous. 

The  hydrochloride  of  the  hexamethyl  dye  has  manifestly  the  con- 
stitution : 

V<C6H4.N(CH3)2.C1 


the  H-atom  of  the  combined  HCl  breaking  off  with  the  hydroxy!  of  the 
compound  as  water. 

Hexamethyl-carbinol  no  longer  contains  an  amido-hydrogen 
atom,  in  consequence  of  which  any  further  methyl  chloride  or 
iodide  cannot  effect  an  exchange  of  hydrogen  for  alkyl  but 
can  only  form  an  addition-compound.  Such  addition  effects  a 
change  of  colour  from  violet  to  green ;  thus  the  compound 
C,9Hi2(CH3)6N3Cl,  CH3CI  is  the  dye  Methyl  green  or  Light 
green. 

2.  Phenylated-rosanilines.  By  the  successive  entrance  of 
phenyl  groups  into  rosaniline,  there  result  in  the  first  instance 
violet  dyes,  which  change  to  blue  when  three  phenyl  groups 
have  entered.  Triphenyl-rosaniline  hydrochloride  or  ^'aniline 
blue  "  is  a  beautiful  blue  dye,  insoluble  in  water  but  soluble 
in  alcohol.  It  is  prepared  by  heating  rosaniline  with  aniline 
in  presence  of  benzoic  acid,  when  ammonia  is  eliminated ;  or 
by  the  oxidation  of  an  aniline  already  phenylated,  i.e.  diphenyl- 
amine,  e.g.  by  means  of  oxalic  acid.  The  latter  supplies  the 
methane  carbon  atom,  and  the  beautiful  diphenylamine 
blue "  or  Sprit  blue  which  results  is  a  para-rosaniline 
derivative. 

The  dyes  which  are  insoluble  in  water  are  rendered  soluble 
by  sulphurating  them,  in  which  condition  they  form  the 
Alkali  blue,  Water  blue  and  Light  blue  etc.  of  commerce. 
"Acid  fuchsine,"  Fuchsine  S,  "Acid  violet"  and  "  Acid  green,'* 
which  are  employed  technically,  are  sulpho-salts  of  this  kind. 


454 


XXIX.  TRIPHENYL-METHANE  GROUP. 


3.  Trioxy-triphenyl-methane,  CH(C6H4.0H)3  (the  Aurin 
group). 

Rosolic  acid  was  first  observed  by  Runge  in  1834. 
The  oxygenated  analogues  of  para-rosaniline  and  rosaniline 
are  Aurin,  C^gHi^Og,  and  Rosolic  acid,  CgoH^gOg ; 

C^CeH^.OH  C^C.H^.OH 
I  ^CqH^.O  j  XH3(CH3).0 

Aurin.  Rosolic  acid. 

These  likewise  possess  the  dye-character,  but,  instead  of 
being  basic,  they  are  acid  dyes  (phenol  dyes) ;  they  are  of  far 
less  value  than  the  nitrogenous  dyes  which  have  been  already 
described. 

They  are  formed  when  the  diazo-compounds  of  para-rosaniline,  etc. 
are  boiled  with  water  (Caro  and  Wanklyn,  1866) : 

C(OH)(C6H4-N=N'-S04H)3  +  3H20  =  C(OH)(C6H4.0H)3  +  3N2  +  3H2S04; 
C(OH)(C6H4.0H)3  =  C(C6H4.0H)2(C6H4.0)  +  H2O. 

(The  carbinol  which  must  be  produced  here  in  the  first  instance  is 
incapable  of  existence,  and  gives  up  HgO. )  The  constitutional  formulae 
just  given  follow  from  this  close  relation  to  the  rosanilines. 

Aurin  is  also  obtained  on  heating  phenol  with  oxalic  and  sulphuric 
acids  to  130-150°  (Kolbe  and  Schmitt,  1859),  the  oxalic  acid  yielding  the 
methane-carbon ;  rosolic  acid  results  in  an  analogous  manner  from  a 
mixture  of  phenol  and  cresol  with  arsenic  and  sulphuric  acids.  Phenol 
by  itself  yields  no  rosolic  acid  upon  oxidation. 

Aurin  and  rosolic  acid  crystallize  in  beautiful  green  needles  or 
prisms  with  a  metallic  glance,  dissolve  in  alkalies  with  a  fuchsine-red 
colour,  and  are  thrown  down  again  from  this  solution  by  acids.  The 
alkaline  salts  are  decidedly  unstable,  aurin  being  but  a  weak  phenol 
at  the  same  time  it  possesses  a  slightly  basic  character.  An  ammonium 
salt  is  known,  which  crystallizes  in  dark  red  needles  with  a  blue  shim 
mer.  Upon  reduction  there  are  formed  the  leuco-compounds  Leucaurin, 
CH(C6H4.0H)3,  and  Leuco-rosolic  acid,  GH(C6H4.0H)2(C6H3[CH3].OH), 
both  of  which  crystallize  in  colourless  needles  of  phenolic  character. 
Superheating  with  water  converts  aurin  into  p-dioxy-benzophenone, 
CO(CgH4.0H)2,  and  phenol;  superheating  with  ammonia,  into  para- 
rosaniline. 

Pittacall  or  euj^^ittone,  which  is  present  in  beech-wood  tar,  is  a  hexa- 
methoj^lated  aurin,  Ci9H8(OCH3)603. 


PHTHALOPHENONE  ;  PHTHALEINS  ;  PHTHALINES.  455 


4.  Triphenyl-methane-carboxylic  acid  (the  Bosin  group). 

(Cf.  Baeyer,  A.  183,  1 ;  202,  36). 

Triphenyl-methane-carboxylic  acid,  CH(C6Hg)2(C6H4.C02H),  results 
from  the  reduction  of  phthalophenone  (see  below),  and  yields  triphenyl- 
m  ethane  by  the  separation  of  COg.  It  crystallizes  in  colourless  needles, 
M.  Pt.  115°. 

Triphenyl-carbinol-o-carhoxyllc  acid,  C(OH)(C6Hg)2(C6H4.  CO2H).  The 
anhydride  of  this  acid,  which  is  termed  Phthalophenone,  is  obtained  by 
heating  phthalic  chloride  with  benzene  and  ALClg  (A.  202,  50),  and 
forms  plates,  M.  Pt.  115°.  The  acid  itself  is  incapable  of  existence,  but 
its  salts  are  got  by  dissolving  the  anhydride  in  alkalies.  Phthalophenone 
is  on  the  one  hand  a  triphenyl-methane  derivative  and  on  the  other 
a  derivative  of  phthalic  acid,  in  accordance  with  the  constitutional 
formula : 

n  TT  ^^(^^6115)2^0      —  r!-^(^6H5)2 
^%^4<^    CO  -  |'^C6H4-CO; 

I  6 


it  is  to  be  looked  upon  as  diphenyl-phthalide  (see  phthalide,  p.  424). 

Phthaloplienone  is  the  mother  substance  of  a  large  series  of 
dyes,  which  are  derived  from  it  by  the  entrance  either  of 
hydroxyl  or  of  amidogen.  They  are  prepared  by  the  action  of 
phenols  upon  phthalic  anhydride  and  are  termed  Phthaleins. 
Phenol  and  resorcin,  for  example,  yield  the  compounds : 

c.H.<«(«.=sOH),>o  c.h.C(c:h:(OH)>o)>; 

Phenol-phthalein.  Fluorescein, 
in  the  latter  case  a  molecule  of  water  is  split  off  from  two 
hydroxyls  of  the  two  resorcin  residues.  Phthalems  of  this 
kind  (being  oxy-phthalophenones)  are  converted  by  reduction 
into  the  oxy-derivatives  of  triphenyl-carboxylic  acid,  which 
are  termed  Fhthalines e.g  phenol-phthalein  into  dioxy- 
triphenyl-methane-carboxylic    acid    (i.e,  phenol-phthaline), 

CH^^^^^^^^^2^.    The  phthalines  are  colourless,  and  are  to 

be  looked  upon  as  leuco-compounds  of  the  phthaleins.  The 
phthalems  include  among  themselves  many  dyes  which  are  of 
technical  value,  e.g.  the  eosins  {Caro,  Baeyer^  1871). 


456 


XXIX.  TRIPHENYL-METHANE  GROUP. 


Phenol-phthalein,  C20H14O4,  is  prepared  by  heating  phthalic  an- 
hydride with  phenol  and  sulphuric  acid  or,  better,  stannic  chloride  (or 
oxalic  acid)  to  115-120°.  It  also  results  upon  nitrating  diphenyl- 
phthalide,  reducing  the  two  substituting  nitro-groups  to  amido-ones, 
and  transforming  these  into  hydroxyl  by  diazotizing  (A.  202,  68).  It 
crystallizes  from  alcohol  in  colourless  crusts ;  in  water  it  is  nearly 
insoluble,  but  it  dissolves  in  alkalies  with  a  beautiful  red  colour  which 
vanishes  again  on  the  addition  of  acids  ;  it  is  thus  a  valuable  indicator 
(B.  17,  1017,  1097).  It  yields  a  Di-acetyl  derivative  and  is  reduced  by 
potash  and  zinc  dust  to  : 

Phenol-phthaline  (colourless  needles),  which  dissolves  in  alkali  to 
a  colourless  solution,  but  is  readily  reoxidized  in  this  solution  to 
phthalein. 

riuorescein  or  resorcin-pMhalein,  C^qH^cP^  +  HgO,  is  pre- 
pared by  heating  phthalic  anhydride  and  resorcin  to  200°.  It 
forms  a  dark  red  crystalline  powder,  and  dissolves  in  alcohol 
with  a  yellow-red  colour,  and  in  alkalies  with  a  red  colour  and 
splendid  green  fluorescence.  It  is  reducible  to  the  phthaline 
"  Fluorescin,"  and  yields  with  bromine  red  crystals  of  tetra- 
bromo-fluorescein,  whose  potassium  salt,  CgoHgBr^O^Kg,  is  the 
magnificent  dye  Eosin.  Fluorescing  dyes  are  likewise  formed 
in  an  analogous  manner  from  all  the  derivatives  of  1 :  3-dioxy- 
benzene,  in  which  position  5  is  unoccupied. 

Instead  of  phthalic  acid  itself,  chlorinated  or  brominated,  etc. 
phthalic  acids  may  be  employed,  so  that,  by  gradually  increasing  the 
amount  of  halogen  present,  a  whole  series  of  yellow-red  to  violet-red 
eosins  can  be  prepared,  e,g,  tetrabrom-iodo-eosin ;  these  are  known 
under  the  names  of  Erythrosin,  Eose  de  Ben  gale,  Phloxin,  etc.  It  is 
worthy  of  note  here  that  many  other  dibasic  acids,  e.g.  succinic  and 
maleic,  are  capable  of  yielding  fluorescing  compounds. 

Further,  m-amido-phenol  and  m-dimethyl-amido-phenol  show  a 
behaviour  towards  phthalic  anhydride  similar  to  that  of  resorcin.  The 
dye  Rhodanin,  C2oHio03[N( 0113)212,  which  is  prepared  from  m-dimethyl- 
amido-phenol,  is  derived  from  fluorescein  by  the  exchange  of  both  of  the 
two  hydroxyls  for  two  N'(CH3)2-groups,  and  is  therefore  not  a  phenol 
but  a  basic  dye  of  beautiful  shade. 

Gallein,  C20H10O7,  is  obtained  in  an  analogous  manner  from  pyro- 
gallol  and  phthalic  anhydride ;  it  dissolves  in  alkalies  with  a  blue 
colour.  Gallein  contains  two  atoms  of  hydrogen  less  than  the  normal 
phthalein  of  pyrogallol ;  as  in  the  case  of  coerulignone,  two  "  super- 
oxide "  oxygen  atoms  are  assumed  here. 

Its  phthaline,  Gallin,  C20HJ4O7,  is  transformed  by  concentrated 


dibenzyl;  stilbene. 


457 


sulphuric  acid  into  the  phthalidine  "  Coerulin,  CgoHigOg,  which  yiehls 
the  "  phthalidein"  Coerulein,  CsoHgOg,  a  valuable  olive-green  dye,  upon 
oxidation.  The  mother  substance  of  both  the  latter  compounds  is 
phenyl-anthranol  (p.  473).    For  details,  see  A.  209,  249. 

XXX.  DIBENZYL  GROUP. 

The  modes  of  formation,  etc.  of  the  members  of  the  dibenzyl 
group  show  that  the  two  benzene  nuclei  in  them  are  connected 
together  by  two  carbon  atoms ;  all  of  them  are  transformed 
into  benzoic  acid  upon  oxidation. 

Summary. 

CgHg — CH2 — CH2 — CgHg   CgHg — CH=CH — CgHs    CgHg — C=C — CgHg 
Dibenzyl.  Stilbene.  Tolane. 

CeHg— CH2-CO— CfiHg         C6H5-CH(OH)— CH(OH)— CgHg 
Desoxy-benzoin.  Hydrobenzoin. 

C6H5-CH(OH)-CO— CgHg  CeHg— CO— CO— CgHg 

Benzoin.  Benzile. 

Dibenzyl  may  be  designated  as  symmetrical  diphenyl-ethane 
(for  the  unsymmetrical  compound,  see  p.  445),  stilbene  as 
5-diphenyl-ethylene,  and  tolane  as  diphenyl-acetylene. 


Dibenzyl,  C14H14.  When  benzyl  chloride  (2  mols.)  is  treated  with 
sodium,  the  two  liberated  residues  CgHg — CHg —  (benzyl)  join  together 
with  the  formation  of  dibenzyl,  a  hydrocarbon  which  is  isomeric  with 
ditolyl  and  with  phenyl-tolyl-methane.  It  crystallizes  in  needles  or 
small  plates,  M.  Pt.  52°,  and  sublimes  unchanged. 

Stilbene,  diphenyl-ethylene,  C14H12,  forms  monoclinic  plates  or  prisms, 
M.  Pt.  126°,  which  also  boil  without  decomposition.  It  may  be  pre- 
pared e.g.  by  the  action  of  sodium  upon  benzal  chloride  or  oil  of  bitter 
almonds,  or  by  passing  the  vapour  of  toluene  or  dibenzyl  over  heated 
oxide  of  lead,  and  possesses  the  full  character  of  an  olefine,  giving  — 
for  instance —  a  dibromide,  O^^r^ — CHBr — CHBr — CgHg,  with  bromine, 
and  being  converted  into  dibenzyl  by  hydriodic  acid.  ;9-Diamido- 
stilbene,  Ci4EI]o(N  112)2,  disulphonic  acid  are,  like  benzidine, 

mother  substances  of     cotton  dyes"  (see  p.  440).     Just  as  ethylene 


458 


XXX.  DIBENZYL  GROUP. 


bromide  yields  acetylene  when  boiled  with  alcoholic  potash,  so  does 
stilbene  dibromide  yield  : 

Tolane,  C14H10,  which  crystallizes  in  prisms  or  plates,  M.  Pt.  60°. 
Tolane  corresponds  with  acetylene  in  its  properties  in  so  far  that  it 
combines  with  chlorine  to  a  dichloride  and  a  tetrachloride,  and  so  on, 
but  it  does  not  yield  metallic  compounds  since  it  contains  no  "  acetylene 
hydrogen. " 

When  stilbene  dibromide  is  treated  with  silver  acetate  and  the 
resulting  acetic  ether  acted  upon  by  alcoholic  ammonia,  one  obtains 
two  isomeric  substances  of  the  composition  : 

C14H14O2,  =  CoH5-CH(OH)-CH(OH)-C6H5, 

Hydrobenzoin  and  Iso-hydrobenzom.  These  likewise  result  ,  from  the 
action  of  sodium  amalgam  upon  oil  of  bitter  almonds.  The  former 
crystallizes  in  rhombic  plates,  M.  Pt.  133°,  and  the  latter  in  four-sided 
prisms,  M.  Pt.  119°,  which  are  the  more  soluble  of  the  two.  Their 
di-acetyl  ethers  are  also  different.  The  reason  of  the  isomerism  of 
hydrobenzoin  and  iso-hydrobenzoin  is  not  yet  clear ;  possibly  they  are 
only  physically  isomeric  (see  A.  198,  191  and  115). 

The  compounds  Benzoin,  Benzile  and  Desoxy-benzoin,  which  have 
already  been  referred  to  in  the  summary,  are  closely  related  to  one 
another  as  their  formulae  show,  and  can  also  be  prepared  from  bitter 
almond  oil.  The  latter  condenses"  (p.  133)  in  alcoholic  solution,  under 
the  influence  of  potassium  cyanide,  to  benzoin  (2C7HgO,  =  Ci4Hi202), 
which  forms  beautiful  glancing  prisms  ;  nascent  hydrogen  reduces  it  to 
hydrobenzoin,  from  which  it  also  results  upon  oxidation.  It  reduces 
Fehling's  solution  even  at  the  ordinary  temperature,  with  the  formation 
of  benzile. 

Benzile,  CgHg—  CO — CO — CgHg,  is  obtained  by  oxidizing  benzoin  by 
means  of  nitric  acid.  It  crystallizes  in  large  six-sided  prisms,  M.  Pt. 
90^  It  reacts  as  a  double  ketone  with  hydroxylamine,  is  oxidized 
to  benzoic  acid  by  CrOg,  and  reduced  by  nascent  hydrogen — according 
to  the  conditions— either  to  benzoin  or  to  : 

Desoxy-benzoin.  The  latter  forms  large  plates,  M.  Pt.  55°,  and  can 
be  sublimed  or  distilled  unchanged.  It  can  be  prepared  by  the  action 
of  benzene  and  aluminic  chloride  upon  the  chloride  of  phenyl-acetic 
acid  (CgHg — CHg — CO.  CI),  which  is  a  proof  of  its  constitution,  and 
yields  di-benzyl  with  hydriodic  acid. 

Benzilic  acid,  (C6H5)2=C(OH)— CO2H  (p.  445),  results  upon  heating 
benzile  with  alcoholic  potash,  by  a  peculiar  molecular  transformation 
similar  to  that  by  which  pinacoline  is  formed  (p.  192). 

A  series  of  compounds  homologous  with  di-benzyl,  stilbene,  etc. 
is  also  known.  Carboxyl  groups  can  likewise  substitute  in  di-benzyl 
and  stilbene,  with  the  formation  of  phenyl-cinnamic  acid,  diphenyl- 
SQccinic  acid,  stilbene-dicarboxylic  acid,  etc. 


DIPHENYL-DIACETYLENE,  ETO. 


459 


Appendix. 

Further,  two  or  more  benzene  nuclei  may  be  connected  together 
through  more  than  two  carbon  atoms.  In  indigo,  for  example,  the 
two  benzene  residues  are  linked  together  by  four  carbon  atoms,  and 
the  same  holds  good  for  the  hydrocarbon  which  is  its  basis,  viz., 
Diphenyl-diacetylene,  CgHg — C=C— C=C — CgHg  {Baeyer).  This  last 
compound  results  from  the  oxidation  of  copper  phenyl-acetylene, 
CfiHg — C=C — Cu,  with  a  solution  of  potassium  ferricyanide,  crystallizes 
in  long  needles  which  melt  at  88°,  and  combines  with  eight  atoms  of 
bromine  to  an  octo-bromide.  Its  o-Dinitro-derivative,  which  is  pre- 
pared in  an  analogous  manner  from  o-nitro-phenyl-acetylene,  yields 
indigo  when  treated  first  with  sulphuric  acid  and  then  with  sulphide  of 
ammonium  (see  p.  432;  also  B.  15,  53). 

In  Dibenzoyl- acetic  acid,  (CgH5.CO)2=CH— COgH,  a  di-ketonic  acid, 
whose  ether  is  obtained  by  treating  benzoyl-acetic  ether  with  benzoyl 
chloride,  two  benzene  residues  are  connected  together  by  three  carbon 
atoms.  The  free  acid,  which  crystallizes  in  needles,  M.  Pt.  109°,  is 
split  up  into  COg  and  the  di-ketone  Dibenzoyl-methane,  {0^11^0)2=012, 
when  boiled  with  water.  In  the  latter,  a  solid  substance  which  boils 
without  decomposition,  the  hydrogen  of  the  methylene  group  is  re- 
placeable by  metals  (through  the  influence  of  the  two  carbonyls),  so 
that  the  compound  dissolves  in  alkalies  and  is  again  thrown  down  by 
acids.  By  the  further  action  of  benzoyl  chloride  upon  its  sodium 
compound,  we  obtain  Tribenzoyl-methane,  (C6H5.CO)3CH. 

Vulpic  acid,  C19H14O5,  a  lichen  acid,  is  related  to  the  above 
compounds. 


Tetraphenyl-ethane,  {CqI15)2=CR—CB.=(CqHq),2  (large  prisms),  and 
Tetraphenyl-ethylene,  (C6H5)2=C=C=(C6Hg)2  (fine  needles),  are  also 
related  to  dibenzyl ;  both  of  these  go  into  benzophenone  upon  oxidation. 


COMPOUNDS  WITH  CONDENSED  BENZENE 
NUCLEI. 

That  portion  of  coal  tar  which  boils  at  a  high  temperature 
contains  a  number  of  higher  hydrocarbons,  among  which 
may  be  especially  mentioned  naphthalene,  C^^^Hy,  anthracene. 


460 


XXXI.  NAPHTHALENE  GROUP. 


Cj^HjQ,  and  its  isomericle  phenanthrene,  G-^Ji-^Q.  The  first- 
named  is  found  in  the  fraction  between  180-200°,  and  the 
two  latter  in  that  between  340-360°. 

These  compounds  are  of  more  complex  composition  than 
benzene,  the  molecule  of  naphthalene  differing  from  that  of 
the  latter  by  C^Hg,  and  those  of  anthracene  and  phenanthrene 
from  that  of  naphthalene  by  the  same  increment.  They  show 
however  the  most  complete  analogy  to  benzene  as  regards 
behaviour,  so  that  almost  exactly  the  same  varieties  of  com- 
pounds may  be  derived  from  them  as  from  benzene  itself. 

As  a  matter  of  fact  they  are  undoubtedly  benzene  deriva- 
tives, anthracene  yielding  benzoic  acid  upon  oxidation, 
naphthalene  phthalic  acid,  and  phenanthrene  diphenic  acid. 
From  their  modes  of  formation  and  behaviour  it  follows  that 
in  the  building  up  of  their  molecules  the  benzene  residues 
combine  together  in  such  a  manner  that  2  or  (2  x  2)  contiguous 
carbon  atoms  are  common  to  both.  For  further  details  see 
pp.  461  and  470, 

XXXI.  NAPHTHALENE  GROUP. 
Naphthalene. 

Naphthalene,  Ci^Hg,  was  discovered  by  Garden  in  1820.  It 
is  contained  in  coal  tar  and  crystallizes  out  from  the  fraction 
which  distils  over  between  180-200°. 

Formation.  1.  By  exposing  a  large  number  of  carbon  com- 
pounds to  a  red  heat;  thus,  together  with  benzene,  styrene, 
etc.,  by  passing  the  vapours  of  methane,  ethylene,  acetylene, 
alcohol,  acetic  acid,  etc.  through  red-hot  tubes. 

2.  By  leading  the  vapour  of  phenyl-butylene  dibromide, 
CgHg— CH2— CH2— CHBr— CHgBr,  over  quick-lime  raised  to  a  low 
red  heat  (Aronheim)  : 

CioHi2Br2  =  CioHg  +  2HBr  +  Hg. 

3.  By  the  action  of  o-xylylene  bromide  (p.  332)  upon  the  sodium 
compound  of  acetylene-tetracarboxylic  ether  (see  ethane- tetracarboxy lie 


NAPHTHALENE. 


461 


ether,  p.  247),  there  results  " Hydronaphthalene-tetracarboxylic  ether" 
thus  : 


p  ^  /.CH^Br  ^  Na-C(C02R)2 
^6^4<\CH2Br  +  Na-C(C02R)2 


C6H4<^ 


CH2— C(C02R)2 
CH2-C(C02R)2 


+  2NaBr ; 


and  from  this  latter,  by  the  separation  of  the  carboxyl  groups  and  the 
excess  of  hydrogen,  naphthalene  (Baeyer  and  PerJcin,  B.  17,  448). 

4.  a-Naphthol,  CiqH^.OH,  is  produced  by  the  separation  of 
water  from  phenyl-isocro tonic  acid  (Fittig  and  Erdmann,  B.  16, 
43),  and  yields  naphthalene  when  heated  with  zinc  dust.  For 
further  details,  see  below. 

Constitution.  That  naphthalene  contains  a  benzene  nucleus, 
in  which  two  hydrogen  atoms  occupying  the  ortho-position  are 
replaced  by  the  group  (CgH^)",  follows  not  only  from  its 
oxidizability  to  phthalic  acid,  but  also  (e.g.)  from  its  formation 
from  o-xylylene  bromide.  And  that  the  four  carbon  atoms  of 
this  group  are  linked  to  one  another  without  branching  is 
shown  by  the  formation  of  a-napthol  (as  given  above),  from 
which  it  follows  at  the  same  time  that  the  end  C-atom  of  the 
side  chain  takes  hold  of  the  benzene  nucleus  already  present, 
with  the  production  of  a  new  six-cornered  ring : 


HC 


CH  CH 
/\^/\cH 


HC 


va:..../ 

HC  l^^OiC 
(OH) 


CH 

Hi 


HC 
HC 


CH  CH 


^C 

HC  C 
(OH) 


CH 
CH 


Phenyl-isocrotonic  acid.  a-Naphthol. 

That  there  are  actually  two  so-called  "  condensed  "  benzene 
nuclei  present  in  the  naphthalene  molecule  is  a  necessary  con- 
sequence of  the  fact  that  phthalic  acid  or  its  derivatives  ensue 
on  the  breaking  up  of  the  compound,  not  only  from  one  but 
from  both  of  the  six-cornered  rings. 

For  instance,  a-nitro-naphthalene  (p.  464)  allows  itself  to  be  oxidized 
to  nitro-phthalic  acid,  C(.H3(N02)(C02H)2  ;  consequently  the  benzene 
ring  to  which  the  nitro-group  is  linked  remains  intact.  But,  on  reduc- 
ing the  nitro-naphthalene  to  amido -naphthalene  and  oxidizing  the  lattei, 


462 


XXXI.  NAPHTHALENE  GROUP. 


no  amido-phthalic  acid  nor  any  oxidation  product  of  it  is  obtained,  but 
phthalic  acid  itself,  a  proof  that  this  time  the  benzene  nucleus  which 
binds  the  amido-group  has  been  destroyed,  and  that  the  other  has 
remained  intact  {Graebe,  1880 ;  for  an  analogous  proof  by  him,  see 
A.  149,  20). 

Naphthalene  therefore  receives  the  constitutional  formula 

(Erlenmeyer y  : 

H  H 


The  behaviour  of  the  isomeric  tetrahydro-naphthylamines  upon 
oxidation  (p.  464)  is  also  of  great  interest  with  regard  to  the  constitu- 
tion of  naphthalene. 

Properties,  Naphthalene  crystallizes  in  glancing  plates 
which  are  insoluble  in  water,  sparingly  soluble  in  cold  alcohol 
and  ligroi'n,  but  readily  soluble  in  hot  alcohol  and  ether ; 
M.  Pt.  80°,  B.  Pt.  217°.  It  has  a  characteristic  tarry  smell, 
and  is  distinguished  by  the  ease  with  which  it  sublimes  and 
volatilizes  with  steam. 

It  yields  a  molecular  compound,  crystallizing  in  yellow  needles,  with 
picric  acid,  and  takes  up  hydrogen  far  more  readily  than  benzene  does 
to  form  Naphthalene  dihydride,  CioHg.Hg,  and  -tetrahydride,  C10H8.H4, 
both  of  these  being  liquids  of  pungent  odour  which  regenerate  naphtha- 
lene again  when  heated.  By  the  intensive  action  of  hydriodic  acid  and 
phosphorus,  the  second  benzene  nucleus  can  also  be  made  to  take  up 
hydrogen,  so  that  a  hexahydride,  CioHs-^e)  ^^^^  finally  a  dekahydride, 
CioHg.HiQ  result.  It  likewise  yields  addition-products  with  chlorine 
more  readily  than  benzene  does,  e.g.  Naphthalene  dichloride,  CioHg.Cla, 
and  -tetrachloride,  C10H8.CI4  (M.  Pt.  184°);  the  latter  is  oxidized  to 
phthalic  acid  more  easily  than  naphthalene  itself,  hence  that  acid  is 
prepared  from  it  on  the  large  scale. 

Naphthalene  is  principally  used  for  the  preparation  of 
phthalic  acid  (for  eosin,  etc.),  and  of  naphthylamines  and 
naphthols  (for  azo-dyes) ;  also  for  the  carburation  of  illumin- 
ating gas.    It  is  a  powerful  antiseptic. 


or 


6 


3 


NAPHTHALENE  COMPOUNDS. 


463 


Derivatives  of  Naphthalene. 

The  substitution  products  etc.  of  naphthalene  may  be  mono- 
or  di-derivatives,  etc. 

The  mono-derivatives  invariably  exist  in  two  isomeric  forms^  the 
a-  and  l3-compounds,  thus  : 

C10H7CI  ^"j^Chloro-naphthalene.     C10H7NH2  j^^lNaphthylamine. 
C10H7OH  ^;|Naphthol.  C10H7CH3     I  Methyl-naphthalene. 

As  in  the  case  of  the  benzene  compounds,  the  existence  of  two  series  of 
mono-derivatives  here  has  not  only  been  established  empirically,  but  it 
has  also  been  proved  (in  a  manner  similar  to  that  given  on  pp.  307 
et  seq. )  that  the  four  hydrogen  atoms  of  each  of  the  two  groups  have 
an  equal  value  as  regards  one  another,  but  not  as  regards  the  atoms  of 
the  other  group,  so  that  (e.g.)  the  a-position  occurs  four  times  in  the 
molecule,  i.e.  twice  in  each  of  the  benzene  nuclei  {Atterberg). 

The  above  constitutional  formula  for  naphthalene  satisfies  these  con- 
ditions admirably,  since,  according  to  it,  the  positions  1,  4,  5  and  8  are 
severally  equal  and  also  the  positions  2,  3,  6  and  7,  but  not  the  positions 
1  and  2.  The  conception  that  in  the  a-compounds  the  position  1,  4,  5 
or  8  is  occupied  : 


is  due  to  Liebermann  (A.  163,  225),  Eeverdin  and  Nolting  (B.  13,  36), 
and  Fittig  and  Erdmann  (cf.  the  formation  of  a-naphthol,  given  above). 

With  regard  to  the  di-derivatives  of  naphthalene,  a  considerable 
number  of  isomerides  of  a  good  many  are  known  ;  according  to  the 
naphthalene  formula,  ten  are  theoretically  possible  in  each  case 
when  the  two  substituents  are  the  same,  and  fourteen  when  they 
are  different. 


Bromo-na^hthalenes, 


a-Bromo-naphthalene,  which  can  be  prepared  directly,  goes  partially 
into  the  /3-compound  when  heated  with  chloride  of  aluminium. 


464 


XXXI.  NAPHTHALENE  GROUP. 


Nitro-naphthalenes, 

a-Nitro-naphthalene,  CioHy.N02  (Laurent,  1835),  results  from 
the  direct  nitration  of  naphthalene.  It  forms  yellow  prisms, 
M.  Pt.  6 1  °,  boils  without  decomposition,  and  goes  into  di-,  tri- 
and  tetra-nitro-naphthalenes  upon  further  nitration.  On 
reduction  it  is  converted  into  a-naphthylamine. 

The  isomeric  /3-Nitro-naphthalene  can  be  obtained  indirectly  by 
diazotizing  /3-naphthylamine,  and  acting  on  the  product  with  sodium 
nitrite  in  presence  of  cuprous  oxide  (see  p.  337) ;  it  crystallizes  in 
bright  yellow  needles. 

Naphthylamines  ;  Naphthalene-sulphonic  acids. 

a-Naphthylamine,  CiqH^.NH2  (Zinin),  forms  colourless 
needles  or  prisms  readily  soluble  in  alcohol;  M.  Pt.  50°, 
B.  Pt.  300°.  It  can  also  be  easily  prepared  by  heating 
a-naphthol  with  the  double  compound  of  chloride  of  calcium 
and  ammonia  (while  aniline  can  only  be  got  from  phenol  in  a 
similar  manner  with  difficulty) : 

CioH^.OH  +  NH3  =  CioH^.NH^  +  H^O. 

It  possesses  a  disagreeable  fsecal-like  odour,  sublimes  readily, 
and  turns  brown  in  the  air.  Certain  oxidizing  agents,  such  as 
ferric  chloride,  produce  a  blue  precipitate  with  solutions  of  its 
salts,  while  others  give  rise  to  a  red  oxidation  product;  chromic 
anhydride  oxidizes  it  to  a-naphthoquinone.  In  other  respects 
it  is  very  like  aniline. 

The  isomeric  ^-Naphthylamlne,  CjQH^.NHg  (Liehermann, 
1876),  is  most  conveniently  prepared  by  heating  /5-naphthol 
either  in  a  stream  of  ammonia  or  with  the  double  compound 
of  zinc  chloride  and  ammonia.  It  crystallizes  in  glancing 
mother-of-pearl  plates,  M.  Pt.  112°,  and  has  no  odour.  It  is 
more  stable  than  a-naphthylamine  and  is  not  coloured  by 
oxidizing  agents. 

Both  of  these  naphthylamines  can  be  converted  into  tetrahydro- 
compounds  by  the  action  of  sodium  and  amyl  alcohol  [i.e.  nascent 
hydrogen)  upon  them.    While,  however,  Tetrahydro- a-naphthylamine 


NAPHTHYLAMINES. 


465 


still  resembles  its  mother  substance  closely  in  most  of  its  properties, 
Tetrahydro-/3-naphthylamine  possesses  a  character  somewhat  like  that 
of  ethylamine.  The  latter  is  very  strongly  basic,  has  an  affinity  for 
carbonic  acid  and  cannot  be  diazotized,  yielding  on  the  contrary 
a  very  stable  nitrite.  The  a-compound  is  oxidizable  to  adipic 
acid  (p.  228),  and  the  ^-compound  to  carbo-hydrocinnamic  acid," 
C6H4<^^2— COgH^     -p^^^  justified  in  concluding 

that  in  the  jS-compound  it  is  the  benzene  nucleus  to  which  the  amido- 
group  is  joined  which  has  taken  up  hydrogen,  but  in  the  a-compound, 
on  the  contrary,  the  other  benzene  nucleus  [Bamberger  and  Midler, 
B.  21,  847,  1112,  etc.). 

From  both  naphthylamines  there  are  derived,  as  in  the  benzene 
series,  Methyl-  and  Dimethyl-naphthylamines,  Phenyl-a-  and  -j8-naph- 
thylamines  (which  are  of  technical  importance),  Nitro -naphthylamines, 
Diamido-naphthalenes  or  Naphthylene- diamines,  CioH6(NH2)2,  Diazo- 
compounds  (which  are  in  every  respect  analogous  to  the  diazo-com- 
pounds  of  benzene,  especially  in  their  capability  of  yielding  azo-dyes), 
Diazo-amido-compounds,  etc. 

The  Diazo-amido-naphthalene,  C10H7 — 1^=]^ — NH— C10H7,  which 
results  from  the  action  of  NgOg  upon  a-naphthylamine,  readily  under- 
goes a  molecular  transformation  (like  the  corresponding  benzene 
compound)  into  Amido-azo-naphthalene,  C10H7 — N=N — CioHg.NHg. 
This  latter  compound  crystallizes  in  brownish-red  needles  with  a  green 
metallic  glance,  and  can  be  diazotized,  its  diazo- compound  yielding 
a -Azo -naphthalene,  C10H7 — N=N — O^qK,^  (red  to  steel-blue  glancing 
prisms),  when  boiled  with  alcohol.  This  last,  which  can  either  not  be 
prepared  at  all  or  only  with  great  difficulty  by  the  methods  which 
hold  good  for  azo-benzene,  is  in  its  turn  capable  of  forming  a  hydrazo- 
compound,  Cn)H7— ^^H — NH — C10H7,  which  undergoes  a  molecular 
transformation  with  acids  into  bases  of  the  nature  of  benzidine,  e.g, 
Naphthidine,  (CioH6)2(NH2)2,  etc. 

The  two  Naphthalene- sulphonic  acids,  CioH7(S03H),  which  are 
crystalline  hygroscopic  substances  obtained  by  heating  naphthalene 
with  concentrated  H2SO4,  and  of  which  the  a-acid  changes  into  the 
/5-one  when  warmed  with  sulphuric  acid,  yield  the  two  naphthols 
when  fused  with  alkalies,  and  the  two  Cyano -naphthalenes,  C10H7.  CN, 
when  heated  with  potassium  cyanide;  these  last  are  crystalline  com- 
pounds which  distil  unchanged. 

Naphthylamine-sulphonic  acids,  e.g.  G^^q(1^'R^{^0^\  are 
known  in  large  number.  Naphthionic  acid  (NH2 :  SO3H  -1:4) 
results  upon  sulphurating  a-naphthylamine ;  it  is  employed 
in  the  preparation  of  azo-dyes. 


(506) 


2G 


466 


XXXI.  NAPHTHALENE  GROUP. 


Najphthols, 

a-  and  /5-Naphthols,  CjqH^.OH,  which  are  present  in  coal 
tar,  can  be  easily  prepared,  not  only  from  the  naphthalene- 
sulphonic  acids  as  above,  but  also  by  diazotizing  the  naphthyl- 
amines.  They  crystallize  in  glancing  plates  of  a  phenolic 
odour,  and  are  readily  soluble  in  alcohol  and  ether  but  only 
sparingly  in  hot  water.  a-Naphthol  (Griess,  1866)  has  the 
M.  Pt.  95'  and  B.  Pt.  279^  while  /3-naphthol  (Schdffer,  1869) 
has  the  M.  Pt.  122°  and  B.  Pt.  286° ;  both  of  them  are  readily 
volatile.  They  possess  a  phenolic  character  but  nevertheless 
resemble  the  alcohols  of  the  benzene  series  more  than  the 
phenols,  their  hydroxyl  groups  being  far  more  capable  of 
reaction  than  those  of  the  latter,  e.g.  being  readily  exchange- 
able for  NHg  (see  above). 

Both  of  the  naphthols  yield  Ethyl  ethers,  CioH^.O.CgHg,  Acetyl- 
naphthols,  CioHy.OlCgHsO),  etc.  Ferric  chloride  oxidizes  both,  with 
the  production  of  a  violet  (a)  or  green  (jS)  colour,  to  Dinaphthols, 
C2oHi2(OH)2,  which  correspond  to  the  diphenols  (p.  438)  and  are 
derivatives  of  dinaphthyl. 

From  the  naphthols,  as  from  the  phenols,  there  are  derived  Nitro-, 
Dinitro-,  Trinitro-  and  Amido-compounds,  etc.  The  calcium  salt  of 
Dinltro-a-naphthol,  CioH5(N02)2.0H,  is  known  as  Martins^  yellow  or 
naphthalene  yellow,  and  its  sulphonic  acid,  Naphthol  yellow  S  or  fast 
yelloiv,  is  also  a  valuable  yellow  dye. 

Amido-naphthols,  CioH6(NH2)(OH),  result  from  the  nitro-naphthols 
upon  reduction ;  like  the  amido-phenols  they  are  readily  oxidized  in 
the  air.  (NH2  :  OH  in  the  a -compound  =  1  : 4,  in  the  jS- compound 
=  1:2.) 

The  dyes  (e.g.  Orange  II.)  which  are  obtained  by  the 
action  of  diazo -compounds  upon  the  naphthols,  have  been 
already  mentioned  at  p.  370.  Other  azo-dyes  contain 
only  naphthalene  residues,  e.g.  Fast  red  ("  Echtroth "), 
CioH6(S03Na)— N=N— CioHg.ONa,  which  results  from  the 
action  of  diazo-naphthalene-sulphonic  acid  (a  compound 
analogous  to  diazo-benzene-sulphonic  acid)  upon  /5-naphthol. 
For  the  composition  of  Biebrich  scarlet,  etc.  see  p.  372.  A 
series  of  Naphthol-mono-,  -di-  etc.  sulphonic  acids,  which  are 
of  great  technical  value  for  the  preparation  of  azo-dyes,  are 
known. 


NAPHTHOQUINONES. 


467 


Dioxy-naphthalenes  ;  Naphthoquinones, 

Various  Dioxy-naphthalenes,  CioH6(OH)2,  are  known.  Two  of  them, 
the  hydro-naphthoquinones,  are  oxidizable  by  chromic  acid  to  compounds 
of  a  quinonic  nature  (p.  392),  the  naphthoquinones,  just  as  hydro- 
quinone  itself  is. 

a-Naphthoquinone,  CioHgOg,  also  results  from  the  oxidation  of 
naphthalene,  a-naphthylamine,  a-amido-naphthol,  etc.  by  chromic  acid. 
It  crystallizes  in  yellow  rhombic  tablets,  M.  Pt.  125°,  and  is  the  com- 
plete analogue  of  ordinary  quinone,  having  a  similar  odour  and  being 
volatile  with  steam. 

j8-Naphthoquinone,  which  crystallizes  in  yellow-red  plates  and 
blackens  when  heated  to  115-120°,  has  no  odour  and  is  not  volatile, 
being  thus  more  like  phenanthrene-quinone.  These  two  compounds 
receive  the  formula : 


and 

CO 

j8-Naphthoquin  one 

(see  Schultz,  "  Theerf arben, "  1  Aufl.  S.  861  u.  862),  since  they  react 
with  hydroxylamine  to  form  oximes,  the  so-called  Iso-nitroso-naphthols, 
compounds  which  are  also  obtained  by  the  action  of  nitrogen  trioxide 
upon  the  naphthols  themselves. 

Oxy -naphthoquinones,  CjoHgOglOH),  are  likewise  known.  The  ordin- 
ary oxy-naphthoquinone  is  a  hydroxyl  derivative  of  a-naphthoquinone 
(0:0:  OH  =  1:4:2);  Juglone  (yellow  needles)  is  an  isomeric  oxy- 
naphthoquinone  (0:0:  OH  =  1:4:5)  which  occurs  in  nut  shells  and 
has  also  been  prepared  artificially  (B.  20,  934). 

A  Dioxy-naphthoquinone,  CioH402(OH)2,  is  the  naphthazarin "  or 
alizarin  black"  of  commerce,  a  valuable  dye  which  is  prepared  by 
acting  upon  a-dinitro-naphthalene  with  zinc  and  sulphuric  acid,  and 
which  comports  itself  like  the  alizarin  dyes  ;  it  is  the  "alizarin "  of  the 
naphthalene  series  (see  p.  474). 


Homologues  of  Naphthalene  and  Hydrocarbons  related  to  it ; 
Carhoxylic  Acids. 

a-  and  /^-Methyl-naphthalenes,  CioH^.CH^,  and  also  the 
Dimethyl-naphthalenes,  G^^^q{GE.^c^,  are  present  in  coal  tar. 


468 


XXXI.  NAPHTHALENE  GROUP. 


They  may  be  prepared  synthetically  by  methods  analogous  to 
those  applicable  to  the  homologues  of  benzene. 

The  Naphthoic  acids,  CioH7.(C02H),  can  be  obtained  by  saponifying 
the  cyano-naphthalenes  and  also  by  the  other  synthetical  methods  given 
on  pp.  404  et  seq.  ;  they  crystallize  in  fine  needles  sparingly  soluble 
in  hot  water,  and  break  up  into  naphthalene  and  COg  when  distilled 
with  lime.  Among  the  Naphthalene -dicarhoxylic  acids,  CioHg(C02H)2, 
which  are  known  may  be  mentioned  Naphthalic  acid,  which  at  a  some- 
what high  temperature  yields  an  anhydride  similar  to  phthalic  anhyd- 
ride. The  positions  a-a'"  (=  1:8)  are  ascribed  to  its  carboxyls,  this 
being  termed  the  "peri  "-position. 

Phenyl-naphthalene,  Cif^^jiC^R^)^  has  also  been  prepared ;  it  is  a 
compound  built  up  of  a  naphthalene  and  of  a  benzene  nucleus,  and  is 
therefore  analogous  to  diphenyl,  CgHg — CgHg.    The  same  applies  to  : 

Di-naphthyl,  C10H7 — C11H7,  which  yields  derivatives  [e.g.  the  di- 
naphthols  and  naphthidines)  analogous  to  those  of  diphenyl.  Three 
modifications,  the  a-a-,  /3-/3-  and  .a-/3- compounds,  are  theoretically 
possible. 

Another    derivative    of   naphthalene    is   Acenaphthene,  C12H10, 
CH 

=  CioH6<C^TT^)  which  is  found  in  coal  tar.    It  crystallizes  in  colourless 
CH2 

prisms,  M.  Pt.^95°,  B.  Pt.  277°. 


Appendix,  Indonaphthene ;  Thiophthene. 

The  hypothetical  Indonaphthene,  also  termed  Indene,  CgHg,  is  very 
similar  to  naphthalene  in  constitution,  thus  : 


Derivatives  of  it  have  been  prepared  synthetically  (B.  17,  125  ,  20, 
1574,  etc.). 

Further,  there  is  a  compound  bearing  the  same  relation  to  naph- 
thalene that  thiophene  does  to  benzene,  viz.  : 


Thiophthene,  C4H6S2,  = 


ANTHRACENE. 


469 


which  may  be  looked  upon  as  resulting  from  the  condensation  of  two 
thiophene  nuclei.  It  is  prepared  by  heating  citric  acid  with  phosphorus 
trisulphide  (B.  19,  2444),  and  is  an  oily  liquid  whose  B.  Ft.  (225°)  differs 
only  in  slight  degree  from  that  of  naphthalene.  Thionaphthene, 
already  described  on  p.  437,  stands  midway  between  thiophthene  and 
naphthalene. 


XXXII.  THE  ANTHRACENE  AND  PHENAN- 
THRENE  GROUPS. 

A.  Anthracene. 

Anthracene,  C^^H^q  {Dumas  and  Laurent^  1832;  Fritzsche, 
1857).  Formation.  1.  Together  with  benzene  and  naph- 
thalene by  the  destructive  distillation  of  coal  and,  generally, 
by  the  pyrogenous  reactions  which  give  rise  to  these  products, 
e.g.  by  passing  CH^,  G^^,  C2H2,  the  vapour  of  alcohol,  etc. 
through  red-hot  tubes  (c£  p.  460). 

2.  By  heating  o-tolyl-phenyl  ketone  with  zinc  dust  (B.  7,  17) ; 

3.  Together  with  dibenzyl,  by  heating  benzyl  chloride  with  water  to 
200°  (B.  7,  248)  : 

4C6H5-CH2CI  =  C14H10  +  C14H14  +  4HC1. 

4.  From  o-bromo-benzyl  bromide  and  sodium  in  ethereal  solution  ; 
here  hydro-anthracene  is  at  first  formed,  and  this  is  converted  by 
oxidation  (which  is  partly  spontaneous  during  the  above  reaction)  into 
anthracene  (B.  12,  1965): 

^«H4<cH,Br  +  ^'^ir>^6H4  +  4Na  =  0,^,<c^^^,^^  +  ^NaBr  ; 
C6H4<gg^>CeH,  -  H,  =  CeH,<^JJ>C,H,. 

5.  By  heating  benzene  with  symmetrical  tetrabromo-ethane  and 
aluminic  chloride  (B.  16,  623)  : 

BrCHBr  +  ^""^  "  ^^^^^^^CH" 

6.  When  phthalic  anhydride  is  heated  with  benzene  and 


470  XXXII.  ANTHRACENE  AND  PHENANTHRENE  GROUPS. 


chloride  of  aluminium,  o-benzoyl-benzoic  acid  results,  and  from 
this,  on  heating  with  phosphoric  anhydride,  anthraquinone 
{Behr  and  v.  Dorp,  B.  7,  578) ;  the  latter  goes  into  anthracene 
upon  reduction  with  zinc  dust : 


7.  From  alizarin  by  means  of  zinc  dust  (see  p.  474). 

Constitution.  From  the  above  modes  of  formation  and  from 
its  relation  to  anthraquinone,  whose  constitution  follows  e.g. 
from  mode  of  formation  6,  the  anthracene  molecule  is  seen  to 
contain  two  benzene  nuclei,  CgH^,  joined  together  by  a  middle 
group,  CgHg.  The  carbon  atoms  of  this  middle  group  are  like- 
wise linked  together,  as  is  seen  from  mode  of  formation  5,  and 
take  up  the  o-position  with  regard  to  each  other  on  one  or 
other  of  the  benzene  nuclei  (on  one  nucleus  according  to 
methods  of  formation  2  and  6,  and  on  the  other  according  to 
method  4 ;  for  further  proofs  of  this,  see  e.g.  v.  Pechmann,  B. 
12,  2124).  The  constitution  of  anthracene  is  thus  the  follow- 
ing (Graebe  and  Liebermann,  A.  Suppl.  7,  313) : 


HC 


HC 


H 
C 


c 

H 


H 
C 


c 

H 


H 
C 


C 

H 


CH 


CH 


The  two  carbon  atoms  of  the  middle  group  thus  form  a  new  hexagon- 
ring  with  the  carbon  atoms  of  the  benzene  nuclei  to  which  they  are 
linked,  so  that  anthracene  may  also  be  looked  upon  as  being  built  up 
by  the  conjunction  of  three  benzene  nuclei. 

Properties  and  Behaviour.  Anthracene  crystallizes  in  colour- 
less plates  which  show  a  magnificent  blue  fluorescence.  It  is 
insoluble  in  water  and  only  sparingly  soluble  in  alcohol  and 
ether,  but  readily  so  in  hot  benzene;  M.  Pt.  213°,  B.  Pt. 


DERIVATIVES  OF  ANTHRACENE. 


471 


above  360°.  With  picric  acid  it  yields  an  addition  compound 
crystallizing  in  beautiful  red  needles. 

Anthracene  is  transformed  by  sunlight  into  (the  polymeric  ? )  Para- 
anthracene,  (Ci4Hio)x.  It  takes  up  in  the  first  instance  two  atoms  of 
hydrogen  when  reduced  {e.g.  by  hydriodic  acid  and  phosphorus),  with 
the  formation  of  Anthracene  dihydride,  Ci4H^o-H2  (see  above,  mode  of 
formation  4).  This  latter  crystallizes  in  white  plates,  readily  soluble 
in  alcohol,  M.  Pt.  107° ;  it  sublimes  easily  and  distils  without  decom- 
position, but  goes  back  into  anthracene  at  a  red  heat  or  when  warmed 
with  concentrated  sulphuric  acid.    It  has  the  constitution  : 

A  Hexa-hydride,  Ci4Hio.Hg,  is  also  known. 


Derivatives  of  Anthracene. 

Theoretically  three  isomeric  mono-derivatives  are  possible  in 
each  case,  viz.,  the  a-,      and  y-compounds  : 


a"      y'  a' 


since,  in  the  graphical  formula  given  on  the  preceding  page, 
1  =  4  =  5  =  8  =  a,  2  =  3  =  6  =  7  =  y8,  and  9  =  10  ==  y.  The 
observed  facts  are  in  complete  accordance  with  this. 

The  position  of  the  substituting  group  can  usually  be  determined 
either  by  the  behaviour  of  the  substance  in  question  upon  oxidation,  e.g, 
if  it  be  in  the  7-position  it  will  be  eliminated  with  the  formation  of 
anthraquinone  ;  or  it  is  arrived  at  from  the  synthesis  of  the  compound, 
e.g.  in  the  case  of  alizarin,  whose  formation  from  pyrocatechin  and 
phthalic  acid  shows  that  its  two  hydroxy  Is  are  contained  in  one  and  the 
same  benzene  nucleus. 

Anthraquinone,  GqHl^(C0)2Gq}1^,  in  which  the  hydrogen 
atoms  9  and  10  are  replaced  by  two  atoms  of  oxygen,  only 
yields  two  isomeric  mono-derivatives  in  each  case.  Isomeric 
di-derivatives  may  exist  in  very  large  number. 


472  XXXII.  ANTHRACENE  AND  PHENANTHRENE  GROUPS. 

Summary  of  the  most  important  derivatives  of  Anthracene. 


C^^H^Cl  l^'l^lo^o-,  Dichloro-,  and 
^i4„8   2  I Dibromo-anthracenes 

C14H9.NO2,  unknown. 


C„H,<^^>CeH3.0H  "jAnthrol. 


C14H9.NH2,  Anthramine 

1^  ^'     ^    \  onic  acid. 

r  TT  ^QH  TT\  j3-Anthracene- 
Oi4n8i^U3ti)2|    disulphonic  acids. 

Ci4H9(OH),  Oxy -anthracenes : 

CH 

C6Er4<^^Qjj^>C6H4,  Anthranol  (7). 


Hydro-compound  :  CQR4<.Q^lQ^y>^6^^^  ^oUy)!^ 
Ci4H8(OH)2,  Dioxy -anthracenes : 


C6H4<^  •  J       ^C6H4,  Anthra-hydroquinone  ( isomers 
C14H8O2,  Anthraquinone  : 


Rufol,  FlavolA 
Chrysazol.  / 


r«  Tin  /Qr»  TT\  fAnthraquinone- 

Oi4±i6U2(bU3±l)2        pjjQ^.^  ^^^^^ 


C6H4<^^(^^KC6H4,  Oxanthranol. 


Ci4H702(OH),  Oxy-anthraquinones  : 

C6H4(CO)2C6H3(OH)  :  a  =  Erythro-oxy-,  /3  =  Oxy-anthraquinone. 

Ci4H602(OH)2,  Dioxy -anthraquinones : 

C6H4(CO)2C6H2(OH)2 ;        =  Alizarin,  aa'  =  Quinizarin,  a^'  =  Purpuro- 

xanthine,  etc. 

C6H3(OH)(CO)2C6H3(OH) :  Anthraflavic  acid,  Iso-anthraflavic  acid,  Anthra- 

rufin,  Chrysazin,  etc. 

Ci4H502(OH)3,  Trioxy -anthraquinones : 

C6H4(CO)2C(5H(OH)3 :  a^a'  =  Purpurin. 

Isomers  :  Flavo-purpurin,  Anthra-purpurin,  etc, 
Tetroxy-anthraquinones :  Anthrachrysone,  Rufiopin. 
Hexoxy -anthraquinone :  Rufigallic  acid. 


Ci4H9(CH3),  Methyl-anthracenes. 

Ci4H9(C6H6),  Phenyl-anthracene,  etc. 

p  -p.  /CH2        TT  Alkybhydro- 
^6J=i4<\CHR-^^6^4'  anthracenes. 

p/rvTTv  Phenyl- 


Ci4H8(CH3)2,  Dimethyl-anthracenes. 

XT  /nri  TT\  fAnthracene-carboxylic 
Oi4H9(C02H),|      acids(a,  ft  7). 


CR(OH) 
^6H4<c[c6H5).OH 


anthranols. 
Phenyl- 
\^  TT  oxanthra- 

V><^6^4»  nol 

(Phthalideins), 


DERIVATIVES  OF  ANTHRACENE;  ANTIIRAQUINONE.  473 


Substitution  products  are  obtained  directly  from  these  compounds ; 
they  yield  antliraquinone  upon  oxidation,  and  therefore  contain  the 
halogen  in  the  7-position. 

jS-Anthramine,  C14H11N,  is  obtained  from  /3-anthrol,  C^JIiqO,  and 
ammonia,  anthrol  from  anthracene-sulphonic  acid  and  potash,  and  the 
last-named  acid  by  the  reduction  of  /3-anthraquinone-mono-sulphonic 
acid,  a-  and  j8-Dioxy-anthracenes  are  prepared  by  fusing  the  sulphonic 
acids  with  potash,  and  the  following  substances,  which  stand  midway 
between  hydro-anthracene  and  anthraquinone,  viz.  hydranthranol, 
oxanthranol,  anthranol  and  anthra-hydroquinone  [Liebermann),  by  the 
more  or  less  energetic  reduction  of  anthraquinone.  The  oxy-anthracenes 
appear  to  be  also  present  in  coal  tar.  The  phthalidines  result  from  the 
action  of  concentrated  sulphuric  acid  upon  the  phthalines  (p.  455 ;  cf. 
also  B.  18,  2150),  thus  : 

C6H4<go.O#''^CeH,  -  H,0  =  C,H,<?J^g^'>CeH, 

Triphenyl-methane-carboxylic  acid.  Phenyl- anthranol ; 

they  are  oxidizable  to  the  phthalideins,  e.g.  Coerulein  (p.  457). 
7-Alkylated  anthracenes  are  also  produced  by  the  elimination  of  the 
elements  of  water  from  the  alkylated  hydranthranols,  which  in  their 
turn  are  obtained  from  hydranthranol  by  acting  upon  it  with  alkyl 
iodide  and  potash ;  while  7-phenyl-anthracene  is  got  by  heating  phenyl- 
anthranol  (a  phthalidine)  with  zinc  dust.  For  isomeric  alkyl-anthra- 
cenes,  see  below.  Anthraquinone  and  its  oxy-compounds  are  of  especial 
importance. 


Anthraquinone,  Ci^HgOg  (Laurent,  1834).  Formation  as 
given  above.  It  is  easily  obtained  by  oxidizing  anthracene 
with  chromic  acid  mixture  (which  is  the  method  followed  on 
the  large  scale),  or  with  chromic  anhydride  and  glacial  acetic 
acid,  and  is  also  produced  when  calcium  benzoate  is  distilled. 

It  crystallizes  in  yellow  prisms  or  needles  which  are  soluble 
in  hot  benzene,  sublime  with  great  readiness,  and  are  ex- 
ceedingly stable  as  regards  oxidizing  agents ;  M.  Pt.  277°. 
Hydriodic  acid  at  150°  reduces  it  either  to  anthracene  or  its 
di-hydride,  while  fusion  with  potash  converts  it  into  benzoic 
acid.  It  possesses  more  of  a  ketonic  than  of  a  quinonic 
character  (Zincke,  Fittig),  not  being  reduced  by  sulphurous  acid, 
and  it  gives  an  oxime  with  hydroxylamine. 


474  XXXII.  ANTHRACENE  AND  PHENANTHRENE  GROUPS. 


It  yields  (mono-  and  di-)  bromo-,  nitro-  and  sulpho- compounds. 
Anthraquinone-j8-mono-sulphonic-acid  crystallizes  in  yellow  tablets ;  of 
the  Di-sulpho-acids  we  are  acquainted  with  two  which  are  formed 
directly  from  anthraquinone,  and  two  which  are  produced  by  the 
oxidation  of  the  anthracene-disulphonic  acids. 

Fusion  of  the  sulphonic  acids  with  potash  does  not  generally  yield 
the  analogous  oxy-compounds  in  theoretical  quantity,  oxygen  being 
usually  absorbed  from  the  air  at  the  same  time ;  thus  the  mono-sulphonic 
acids  yield  mono-  and  dioxy-,  and  the  di-sulphonic  acids  di-  and  trioxy- 
anthraquinones.  In  practical  working  the  amount  of  chlorate  of  potash 
required  is  added  to  the  "melt."  Prolonged  fusion  with  potash  gives 
rise  to  decomposition  into  (oxy-)  benzoic  acids. 

Various  Oxy-anthraquinones  can  also  be  prepared  by  the  synthetical 
mode  of  formation  6,  p.  469,  which  applies  in  the  case  of  anthraquinone, 
viz.,  from  phthalic  anhydride  and  the  mono-  or  dioxy-benzenes  (Baeyer 
and  Caro,  B.  7,  792 ;  8,  152),  e.g,  : 

C6H4<go>^  +  C,Il,(OK),  ^  C6H4<gg>CeH2(OH)2  +  H^O  ; 

phenol  yields  by  this  method  the  two  oxy-anthraquinones  (yellow 
needles),  pyro-catechin  (1:2)  yields  alizarin,  hydroquinone  yields 
quinizarin,  and  so  on.  They  are  further  produced  by  fusing  chloro- 
and  bromo-anthraquinones  with  potash,  while  m-oxy-benzoic  acid  can 
be  converted  directly  by  sulphuric  acid  into  anthraflavic  acid,  water 
being  separated  (see  Summary). 

Alizarin,  C^Jifi^,  is  the  most  important  constituent  of  the  • 
beautiful  red  dye  of  the  madder  root  (Rubia  tinctorum),  which 
has  been  known  for  ages,  being  present  in  the  latter  as  the 
readily  decomposable  glucoside,  Ruberythric  acid,  G2qH.28^u 
(p.  513);  in  addition  to  alizarin,  madder  also  contains  purpurin. 
The  preparation  of  alizarin  from  anthracene,  with  the  inter- 
mediate formation  of  anthraquinone-mono-sulphonic  acid  or  of 
dichloro-anthraquinone,  which  was  first  introduced  in  1871 
(Graebe  and  Liebermami,  Caro,  Perking  B.  3,  359 ;  A.  160,  130), 
depends  upon  an  observation  made  by  Graebe  and  Liebermann 
in  1868  (B.  1,  49;  A.  Suppl.  7,  297)  that  alizarin  is  reduced 
to  anthracene  when  strongly  heated  with  zinc  dust. 

It  crystallizes  in  magnificent  red  prisms  or  needles  of  a 
glassy  glance,  which  melt  at  282**  and  can  be  sublimed,  dis- 
solves readily  in  alcohol  and  ether,  only  sparingly  in  hot  water, 
but,  as  a  phenol,  very  easily  in  alkalies  to  a  violet-red  solution. 
It  yields  insoluble  coloured  compounds — the  so-called  "lakes'^ 


PURPURIN,  ETC.  ;  PHENANTHRENE. 


475 


— with  metallic  oxides,  the  alumina  and  tin  lakes  being  of  a 
magnificent  red  colour,  iron  lake  violet-black,  and  lime  lake 
blue.  In  the  Turkey  Red  manufacture,  for  instance,  the 
materials  to  be  dyed  are  previously  mordanted  with  acetate 
of  alumina  or  with  " ricinoleic-sulphuric  acid"  (see  p.  167). 

Nitrogen  tetroxide,  N2C^4»  converts  alizarin  into  /3-Nitro-alizarin  or 
Alizarin  orange,  Ci4H7(N02)04,  a  yellowish-red  dye ;  and  this  latter, 
when  treated  with  glycerine  and  sulphuric  acid  (the  Skraup  reaction, 
p.  492),  yields  Alizarin  blue,  C17H9NO4  (see  quinoline),  which  is  likewise 
a  valuable  blue  dye,  being  used  chiefly  in  the  form  of  the  NaHSOs-com- 
pound. 

Purpurin,  Anthrapurpurin  and  riavopurpurin  are  also 
valuable  dyes  which  are  manufactured  on  a  large  scale. 

The  colouring  power  of  these  compounds  is  connected  with  the  pre- 
sence of  two  hydroxy  Is  in  the  ortho-position  to  one  another. 

Closely  related  to  the  anthracene  dyes  in  properties  is  Galloflavin, 
CisHgOg,  which  is  obtained  by  exposing  an  alkaline  solution  of  gallic 
acid  to  the  action  of  the  air  (Bohn  and  Graehe,  B.  20,  2327). 

Eomologues  of  Anthracene. 
There  are  also  present  in  coal  tar  : 

1.  Methyl-anthracene  (either  a-  or  jS-),  C14H9.CH3,  which  resembles 
anthracene  and  is  oxidizable  to  methyl-anthraquinone ;  M.  Pt.  199°. 

2.  Dimethyl-anthracene,  Ci4H8(CH3)2,  M.  Pt.  224-225°;  isomers  of 
this  compound  have  been  prepared  synthetically. 

The  three  Anthracene-monocarboxylic  acids  which  are  theoretically 
possible  and  also  some  Anthracene-dicarboxylic  acids  are  likewise 
known. 


B.  Phenanthrene. 

Phenanthrene,  Ci^H^o  [Fittig  and  Ostermeyer  (1872),  A.  166, 
361].  This  hydrocarbon  is  found  accompanying  anthracene 
in  coal  tar.  It  crystallizes  in  colourless  glancing  plates,  and 
dissolves  in  alcohol  more  readily  than  anthracene  (with  a  blue 
fluorescence);  M.  Pt.  100°,  B.  Pt.  340°.  It  may  be  separated 
from  anthracene  by  partial  oxidation,  the  latter  being  the  first 

.4 


47G   XXXII.  ANTHRACENE  AND  PHENANTHRENE  GROUPS. 


to  be  attacked,  and  subsequent  distillation.  Oxidizing  agents 
convert  it  into  diphenic  acid  (p.  441).  It  is  employed  in  the 
manufacture  of  printer's  black. 

Formation.  1.  By.  leading  the  vapour  of  toluene,  stilbene,  dibenzyl 
or  o-ditolyl  through  a  red-hot  tube,  thus  : 

C6H4— CH3    _    C6H4— CH  ^ 

C6H4 —  CH3  C'gH4 — CH  ^ 

o-DitoIyl.  Phenanthrene, 

2.  Together  with  anthracene  from  o-bromo -benzyl  bromide  and 
sodium. 

3.  By  distilling  morphine  with  zinc  dust. 

-  Constitution.    The  formation  of  phenanthrene  from  o-ditolyl,  and 

its  oxidation  to  diphenic  acid,  nr^xi^  show  that  it  is  a  diphenyl 

Cgri4 — 002^1 

derivative  and  that  it  contains  one  C-atom  linked  to  each  benzene 
nucleus ;  this  carbon  atom  is  joined  to  the  corresponding  one  by  a 
double  bond,   as  is   shown  e.g.   by  its  formation  from  stilbene, 

^6^5 — CH 
CgHg — CH 

diphenyl  from  benzene.  Since  diphenic  acid  is  a  di-ortho-diphenyl- 
dicarboxylic  acid  {Scliultz,  A.  196,  1  ;  203,  95),  phenanthrene  is 
also  a  di-ortho-derivative  and  possesses  the  following  constitution  : 

CH 

CH 


C6H4-CH 
CgH4 — CH 


According  to  the  above  formula,  the  two  CH-groups  form  a  new 
hexagon  ring  with  the  two  carbon  atoms  of  both  benzene  nuclei  of  the 
diphenyl  to  which  they  are  linked,  so  that  phenanthrene — like  anthra- 
cene— may  be  looked  upon  as  the  product  of  the  coalition  of  three 
benzene  nuclei,  or  of  one  naphthalene  and  one  benzene  nucleus. 

We  are  likewise  acquainted  with  addition  and  substitution  products 
of  phenanthrene,  e.g.  a  tetrahydride,  nitro-,  amido-,  cyano-  and  oxy- 
compounds,  and  sulphonic  and  carboxylic  acids.  Phenanthrol, 
Ci4H9(OH),  is  an  oxy-phenanthrene,  and  Phenanthrene-hydroquinone, 
Ci4H8(OH)2,  a  dioxy-compound  which  goes  upon  oxidation  into  : 


PHENANTHRENE  COMPOUNDS;  FLUORANTHENE,  ETC.  477 


Phenanthrene-quinone,  i  ^  ^    i   ,  which  latter  may  also 
CgH^ — CO 

be  prepared  directly  from  phenanthrene  and  chromic  acid. 
It  crystallizes  in  odourless  orange  needles  which  distil  un- 
changed, but  are  not  volatile  with  steam;  M.  Pt.  198°. 
Phenanthrene-quinone  possesses  the  character  of  a  di-ketone, 
reacting  with  hydroxylamine,  sodium  bisulphite,  etc.,  but  it 
can  be  reduced  to  the  corresponding  hydroquinone  by  sul- 
phurous acid.  It  gives  a  bluish-green  colouration  with  toluene 
containing  thio-tolene,  glacial  acetic  acid  and  sulphuric  acid, 
which  changes  to  violet  after  dilution  and  addition  of  ether, 
i.e.  the  ether  becomes  violet-coloured;  this  is  the  Lauhenheimer 
reaction  (see  p.  298,  also  B.  17,  1338). 

With  o-diamines,  members  of  the  phenazine  group  result 
(p.  501). 


O.  Hydrocarbons  of  more  complex  nature. 

Fluoranthene,  CigHio,  Pyrene,  CiqHiq,  Chrysene,  CjgHia,  and  Retene, 
CisHiS)  are  hydrocarbons  which  have  been  isolated  from  that  portion 
of  coal  tar  which  boils  at  above  360°.  Phenanthrene,  pyrene  and 
fluoranthene  are  also  found  in  *'Stupp"  fat,  i.e.  the  fat  obtained  as  a 
bye-product  from  the  working  up  of  mercury  ores  in  Idria.  They  all 
crystallize  in  white  plates,  sublime  without  decomposition,  and  are 
converted  into  the  corresponding  ketones  upon  oxidation.  Their 
constitution  is  expressed  by  the  following  formulae  (with  regard  to 
that  of  pyrene,  see  Bamberger ,  A.  24 O,  147) : 

C6H4^^  Cg  H4 — CH  Q^S.^- — CH 

C'eHs^Qjj^CH       CioHg — CH         ^^jl^^CgHg— CH 

Fluoranthene.  Chrysene.  Retene. 

Naphtho-anthracene,  which  has  been  prepared  synthetically,  is 
isomeric  with  chrysene  (B.  10,  2209). 


478 


TRANSITION  TO  THE  PYRIDINE  GROUP. 


PYRIDINE  DERIVATIVES,  ALKALOIDS  AND 
COMPOUNDS  RELATED  TO  THEM. 

The  aromatic  compounds  which  have  been  described  up  to 
now  are  derived  from  the  mother  hydrocarbons  : 

Benzene,  CgHg,    Naphthalene,  C-^qH.^,    Anthracene,  Ci^H^q, 

etc. 

But  alongside  of  them  we  have  to  place  several  groups  of 
very  important  nitrogenous  compounds,  which  are  derived 
from  the  mother  substances  : 

Pyridine,  C^H^N,    Quinoline,  CgH^N,    Acridine,  C^gHgN, 

etc. 

in  precisely  the  same  manner  as  the  former  are  from  benzene, 
etc.,  i.e.  through  the  replacement  of  hydrogen  by  halogen, 
NO2,  NH2,  SO3H,  OH,  CH3,  CO2H,  etc. 

The  difference  in  composition  between  these  bases  (among 
one  another)  is  C4H2,  this  being  the  same  as  the  difference 
between  the  mother  hydrocarbons,  from  which  they  may  be 
considered  as  being  derived  by  the  exchange  of  CH  for  N, 
thus : 

CeHg  -  CH  +  N  =  C5H5N. 

Just  as  naphthalene  and  anthracene  are  benzene  derivatives, 
so  are  quinoline  and  acridine  derivatives  of  benzene  on  the 
one  hand  and  of  pyridine  on  the  other ;  the  latter  is  thus  the 
mother  base  of  all  the  classes  of  compounds  which  are  now 
about  to  be  described. 

It  may  be  compared  with  benzene  in  many  points : 
1.  It  is  even  more  stable  than  benzene,  and  is  further 
distinguished  from  the  latter  by  a  greater  indifference  towards 
the  substituting  reagents  sulphuric  and  nitric  acids  and  the 
halogens.  The  first  of  these  sulphurates  only  at  very  high 
temperatures ;  nitro-pyridines  are  as  yet  unknown,  as  are  also 
iodo-pyridines ;  while  chloro-  and  bromo-pyridines  have  so  far 
only  been  prepared  in  small  number.  Neither  pyridine  nor 
its  carboxylic  acids  are  affected  by  nitric  acid,  chromic  acid, 
or  permanganate  of  potash. 


TRANSITION  TO  THE  PYRIDINE  GROUP.  479 

2.  The  behaviour  of  its  derivatives  is  on  the  whole  very 
like  that  of  the  derivatives  of  benzene.  Thus  its  homo- 
logues  (and  also  quinoline,  etc.)  are  transformed  into  pyridine- 
carboxylic  acids  upon  oxidation,  and  these  acids  yield 
pyridine  when  distilled  with  lime,  just  as  benzoic  acid  yields 
benzene. 

3.  The  isomeric  relations  are  also  precisely  similar  to  those 
of  the  benzene  derivatives.  Thus  the  number  of  the  isomeric 
mono-derivatives  of  pyridine  is  the  same  as  that  of  the  isomeric 
bi-derivatives  of  benzene,  viz.,  three ;  and  the  number  of  the 
bi-derivatives  of  pyridine,  with  two  atoms  of  one  and  the  same 
substituent,  the  same  as  that  of  the  benzene  derivatives 
CgHgXXX',  viz.,  six,  and  so  on. 

4.  The  products  of  reduction  are  likewise  analogous.  Just 
as  hexahydro-benzene  results  from  benzene,  so  do  we  obtain 
from  pyridine  (but  more  easily)  hexahydro-pyridine  or  piperi- 
dine,  CgH^jN ;  further,  just  as  naphthalene  yields  tetrahydro- 
naphthalene,  so  does  quinoline  (readily)  tetrahydro-quinoline, 
CgHjjN,  and  acridine  (readily)  (di-)  hydro-acridine,  C^gH^^N, 
which  last  is  analogous  to  anthracene  di-hydride.  Here  also, 
as  in  the  case  of  the  hydrides  of  the  benzene  series,  further 
combination  with  hydrogen  may  take  place,  but  there  is  like- 
wise here  a  tendency  to  the  reproduction  of  the  original 
bases. 

Consequently  the  constitution  of  these  compounds  is  very 
similar  to  that  of  the  benzene  hydrocarbons.  (For  further 
details,  see  pp.  483  and  494.) 

In  contradistinction  to  the  neutral  benzene  hydrocarbons, 
pyridine  and  its  homologues,  etc.,  are  strong  bases,  most  of 
them  having  a  pungent  odour ;  pyridine  is  readily  soluble  in 
water  but  quinoline  only  slightly  so.  They  distil  or  sublime 
without  decomposition,  and  form  salts  with  hydrochloric  and 
sulphuric  acids  which  are  for  the  most  part  readily  soluble, 
while  those  with  chromic  acid,  though  often  characteristic,  are 
usually  only  sparingly  soluble;  also  double  salts  with  the 
chlorides  of  platinum,  gold  and  mercury,  most  of  which 
dissolve  with  difficulty,  and  so  on. 

[Continued  on  p.  480. 


480  TRANSITION  TO  THE  PYRIDINE  GROUP. 

Summary  of  several  Pyridine  and  Quinoline  Derivatives. 


Pyridine 


Chloro-pyridine,  etc. 


Pyridine-sulphonic 
acid  (jS-)  .    .  . 


Oxy -pyridines  (3) . 


Methyl-pyridines  . 
(Picolines)  (3) 

Dimethyl-pyridines 
(Lutidines) 

Trimethyl-pyridines 

Propyl-pyridines  . 


Pyridine-carhoxylic 
acids  (3)  .    .    .  . 

Pyridine-dicarboxylic 
acids  (6)  .    .    .  . 

Picoline-carboxylic 
acids  


Di-pyridine .  .  . 
Di-pyridyl  .  .  . 
Phenyl-pyridines  . 
Piper idine  .    .  . 


C5H5N 
C5H4NCI 

CsH^NCOH) 

CsH^NlCHs) 
CsHsNlCHa)^ 

C5H2N(CH3)3 

CsH^NlCsHy) 
C6H4N(C02H) 

C5H3N(C02H)2 

C5H3N(CH3)(C02H) 

C10H10N2 
O5H4N-C5H4N 
OsH^NlCeHs) 


Quinoline 


Chloro-quinoline,  etc. 

Amido-quinolines  .  . 

Quinoline-sulphonic 
acids  


Oxy-quinolines  .  . 


Methyl-quinolines  . 
(Quinaldine,  etc.) 

Dimethyl-quinolines 

Trimethyl-quinolines 
etc. 


Quinoline-carhoxylic 
acids  

Quinoline-dicarboxylic 
acids  

Quinaldine-carboxylic 
acids  


Di- quinoline .... 
Di-quinolyline  .  .  . 
Phenyl-quinolines  .  . 
Tetrahydro-quinoUne . 


C9H7N 

CgHgNCl 

CoHoNlNHs) 
CgHeNlSOaH) 

CgHeNlOH) 

CgHeNlCHs) 
CANlCHsla 

C9H4N(OH3)3 


C9H6N(C02H) 
C9H5N(C02H), 
CgHsNlCHsllCO: 

C18H14N2 

C9HeN(C6H5) 
CgHnN 


As  bases  they  are  tertiary,  and  therefore  cannot  {e.g.)  be 
acetylated;  they  combine  with  methyl  iodide  to  quaternary 
compounds. 

Pyridine,  quinoline  and  many  of  their  homologues  (and 
also  acridine)  are  found  in  coal  tar  and  in  bone  oil  (oleum 
Dippelii  animale),  from  which  they  can  be  separated  by 
the  addition  of  acids ;  nevertheless  they  cannot,  speaking 
generally,  be  obtained  chemically  pure  even  by  repeated 


ALKALOIDS;  PYRIDINE  GROUP. 


481 


fractionation.  To  prepare  them  pure,  therefore,  recourse 
must  often  be  had  to  synthetical  methods. 

The  quinoline  and  also  the  pyridine  bases  result  from  the 
distillation  of  most  of  the  alkaloids  which  occur  in  nature,  e.g. 
quinine,  cinchonine  and  strychnine,  with  caustic  potash,  etc., 
and  their  carboxylic  acids  from  the  oxidation  of  these  alkaloids. 
It  follows  from  this  that  most  of  the  latter  are  pyridine  deriva- 
tives. 

The  Alkaloids  are  vegetable  bases,  most  of  which  exert  an 
intensely  poisonous  or  curative  action ;  they  are  therefore  of 
great  medicinal  importance.  They  will  be  treated  of  shortly 
here,  partly  under  the  pyridine  derivatives,  and  partly  (where 
their  relation  to  the  latter  is  as  yet  only  slightly  known)  in 
an  appendix.  Certain  alkaloids  {e.g.  caffeine,  p.  284,  and 
choline,  p.  196)  belong  moreover  to  other  classes  of  com- 
pounds. 

The  designation  "alkaloids"  is  now  becoming  limited  to 
the  vegetable  bases  which  are  derived  from  pyridine. 


XXXIIL  THE  PYRIDINE  GROUP,  CAn-sN. 

The  pyridine  group  comprises  pyridine  itself,  together  with 
its  homologues,  carboxylic  acids  and  more  nearly  allied  deriva- 
tives. 

The  homologues  of  pyridine  which  are  obtained  from  coal 
tar  and  bone  oil  are  known  as  Picoline  (CgH^N),  Lutidine 
(C^),  Collidine  (Cg),  Parvoline  (Cg),  Coridine  (C^q),  etc. ;  the 
fractions,  however,  whose  empirical  analyses  agree  with  these 
formulae,  do  not  represent  chemical  individuals,  but  are 
mixtures  of  isomeric  and  also  in  part  of  homologous  bases. 

All  the  homologues  .of  pyridine  are  distinguished  from 
pyridine  itself,  as  those  of  benzene  are  from  the  latter,  by  the 
readiness  with  which  they  are  oxidized  to  pyridine-carboxylic 
acids : 


C,H3N(OH3)(C2H,)  yields  C,H3N(C0,H),. 

(606)  2H 


482 


XXXIII.  PYRIDINE  GROUP. 


Formation.  1.  The  pyridine  bases  result  from  the  destruc- 
tive distillation  of  many  nitrogenous  organic  substances,  hence 
their  presence  in  coal  tar. 

2.  Lutidine  is  obtained,  together  with  other  bases,  on  distil- 
ling cinchonine  with  potash. 

3.  Pyridine  is  got  by  oxidizing  quinoline  to  quinolinic  acid, 
C3H3N(C02H)2,  and  then  breaking  up  the  carboxylic  groups. 

4.  /?-Methyl-pyridine  results  on  distilling  acrolein-ammonia 
(p.  138),  and  collidine  in  an  analogous  manner  from  crotonic 
aldehyde-ammonia  or  aldehyde-ammonia  (p.  132)  {Baeyer^  A. 
155,  283,  297). 

Aldehydine,  CgHiiN,  is  produced  by  heating  ethylidene  chloride  or 
bromide  with  alcoholic  ammonia,  and  /3-methyl-pyridine  by  heating 
glycerine  with  acetamide  and  phosphoric  anhydride. 

5.  When  potassium-pyrrol,  C4H4NK,  is  heated  with  CHCI3,  chloro- 
pyridine,  C5H4CIN,  results  ;  and  when  with  CHgClg,  pyridine. 

6.  Pyridine  is  also  obtained  by  heating  hexahydro-pyridine 
(piperidine)  with  concentrated  sulphuric  acid  to  300°  (Konigs): 

7.  When  the  hydrochloride  of  penta-methylene-diamine, 
C5Hi(,(N  112)2,  is  heated  rapidly,  piperidine  is  produced  {Laden- 
burg,  B.  18,  2956,  3100) : 

C,H,o(NH2)2,  HCl  =  C,H,,N  +  NH.Cl. 

8.  The  compounds  of  the  pyridone  group  (p.  491)  are  transformed 
into  pyridine  derivatives  by  the  action  of  ammonia.  The  amides  of 
citric  acid,  e.g.  the  monamide,  CeHyOeCNHg),  yield  citrazinic  acid 
[dioxy-pyridine-7-carboxylic  acid  {HofmanTi)]  when  heated  with  H2SO4, 
while  acetone-dicarboxylic  acid  yields  trioxy-pyridine  (B.  19,  2694). 

9.  When  aceto-acetic  ether  is  warmed  with  aldehyde-ammonia,  the 
ether  of  "  Dihydro-collidine-dicarboxylic  acid,"  i.e.  a  dihydride  of  tri- 
methyl-pyridine-dicarboxylic  ethyl  ether,  is  produced  (Hantzsch) : 

2C6H10O3  +  CH3.CHO  +  NH3  =  C5N(H2)(CH3)3(C02R)2  +  3H2O. 

This  loses  its  two  '  hydro- '  hydrogen  atoms  when  acted  on  by  ^303, 
and  goes  into  collidine-dicarboxylic  ether,  C5N(CH3)3(C02R)2,  from 
which  collidine  results  on  saponification  and  elimination  of  COg. 

If,  instead  of  aldehyde-ammonia,  the  ammonia  compounds  of  other 
aldehydes  are  used,  one  obtains  analogous  bases  of  the  formula  : 

C5H2N(CH3)3(CnH2„+l). 


pyridine;  formation  and  constitution.  483 

In  the  above  reaction  also  a  molecule  of  aceto-acetic  ether  may  be 
replaced  by  one  of  aldehyde,  when  the  mono-carboxylic  ethers  of 
dimethyl-  etc.  pyridine  are  formed,  thus  : 

CoHioOg  +  2CH3.CHO  +  NH3  =  C5H2NH2(CH3)2.C02R  +  3H2O. 

This  is  a  very  important  synthetical  method  (JIantzsch,  A.  215, 
1,  etc.). 

10.  Trioxy-pyridine  results  from  acetone-dicarboxylic  ether  and 
ammonia. 

11.  Pyridine  is  further  produced  by  oxidizing  its  homologues  to 
carboxylic  acids  and  eliminating  CO2  from  the  latter. 

12.  Conversely,  the  homologues  of  pyridine  are  formed  by  heating 
the  latter  with  alkyl  iodide  to  300°  {Ladenhurg),  a  reaction  analogous 
to  the  production  of  toluidine  from  methyl-aniline. 

Constitution.  The  constitution  of  piperidine  and  pyridine  is 
expressed  by  the  following  formulae  : 

H2  H 
C  C 

H2C/\CH2  HC/\|CH 

and  (1.) 
HaC'v  yCHa  HCsl  ^ICH 

N  N 
H 

Piperidine,  Pyridine. 

That  of  piperidine  follows  from  its  formation  from  penta- 
methylene-diamine : 

CH.<gi;ZCg:ZS|  =  CH,<gg;zC|>NH  +  NH, 

Piperidine  therefore  contains  a  hexagon  ring  made  up  of 
one  imido-  and  five  methylene  groups,  and  is  a  complete 
analogue  of  hexa-methylene ;  it  may  be  designated  penta- 
methylene-imine. 

The  constitution  of  pyridine  follows:  1.  from  its  near 
relation  to  piperidine ; 

2.  from  the  formation  of  pyridine-dicarboxylic  acid  by  the  oxidation 
of  quinoline  (see  above) : 

C9H7N  +  09  =  C5H3N(002H)2  +  H2O  +  2CO2, 

in  conjunction  with  which  are  to  be  taken  the  proofs  of  the  constitution 
of  quinoline  (p.  494) ; 


484 


XXXIII.  PYRIDINE  GROUP. 


3.  from  the  perfect  agreement  with  theory  of  the  observed  isomeric 
relations  (see  below) ; 

4.  from  the  transformation  of  ethyl -pyridine  into  ethyl-benzene  upon 
heating  pyridine  with  ethyl  iodide  (A.  241,  14). 

The  above  constitutional  formula  of  pyridine  was  first  proposed  by 
Korner, 

The  formation  of  collidine-dicarboxylic  ether  (p.  482)  thus  proceeds 
as  follows  (B.  18,  1744): 


I 

OCH 


^  \ 

COgR— CH2        HgC— CO2R     COgR— C       C— CO2B 

I  I  =  I         II  +3H2O  +  H2. 

CH3— CO  OC— CH3         H3C— C       C— CH3 

NH3 

Three  isomeric  mono-derivatives  of  pyridine  are  known  in 
each  case  (p.  479).  This  agrees  with  the  regarding  of  pyridine 
as  a  kind  of  mono-derivative  of  benzene  in  which,  instead  of 
H,  a  CH-group  is  replaced  by  N;  the  mono-derivatives  of 
pyridine  are  thus  comparable  with  the  bi-derivatives  of 
benzene,  and  are  therefore  three  in  number.  They  are 
designated  as  a-,  fS-  and  y-derivatives  of  pyridine,  as  is 
shown  in  the  following  graphical  formula : 


a'\  /a 


(II.) 


In  order  to  determine  the  position  of  any  given  group,  it  is  sought 
to  exchange  it  for  carboxyl ;  should  picolinic  acid  result,  it  fills  the 
a-position,  and  should  nicotinic  or  iso-nicotinic,  then  it  fills  the  p-  or 
7-position  respectively,  since  in  these  acids  the  a-,  /5-  and  7-positions  of 
the  carboxyl  have  been  determined  by  special  means.  (See  Monatsh.  f. 
Chemie,  1,  800;  4,  437,  453,  595;  B.  17,  1518;  18,  2967;  19.  2432). 

Di-derivatives  of  pyridine  containing  in  the  molecule  two  atoms  of 
one  and  the  same  substituent  can  exist  theoretically  in  six  isomeric 
forms.  As  a  matter  of  fact  the  six  dicarboxylic  acids,  for  example,  are 
known  [aa'-,  a(3-,  ay-,  a^S'-,  ^y-  and  /3/3'- ;  see  p.  488). 

The  above  pyridine  formula  (II.)  has  the  advantage  over  (I.)  that  it 
gives  expression  to  the  linking  in  ring  form  of  the  five  carbon  atoms  and 
of  the  nitrogen,  without  rendering  it  necessary  to  take  specially  into 


PYRIDINE. 


485 


account  the  mode  in  which  the  fourth  affinity  of  each  carbon  and  the 
third  affinity  of  the  nitrogen  are  used  (analogously  to  the  hexagon 
formula  of  benzene,  p.  312).  Besides  Korner's  formula,  Dewar's  (1871) 
is  now  frequently  adopted  ;  it  is  : 


The  isomerism  of  picoline,  CgH^N,  with  aniline,  CgHg.NHa,  which 
repeats  itself  in  their  homologues,  is  also  worthy  of  notice. 


Pyridine,  C^H^N  {Anderson,  1846),  may  be  prepared  from 
bone  oil,  and  can  be  obtained  chemically  pure  by  heating  its 
carboxylic  acid  with  lime;  the  ferrocyanide  is  especially 
applicable  for  its  purification,  on  account  of  its  sparing  solu- 
bility in  cold  water.  It  is  also  found  in  the  ammonia  of  com- 
merce. Pyridine  is  a  liquid  of  very  characteristic  odour, 
miscible  with  water  and  boiling  at  114°.  When  sodium  is 
added  to  its  hot  alcoholic  solution,  hydrogen  is  taken  up  and 
piperidine,  C5Hj;,^N,  formed  (Ladenburg  and  Both,  B.  17,  513  ; 
see  also  p.  488). 

When  heated  strongly  with  liydriodic  acid,  pyridine  is  converted 
into  normal  pentane. 

The  ammonium  iodides,  e.g.  C5H5N,  CH3I,  give  a  characteristic 
pungent  odour  when  heated  with  potash,  a  fact  which  may  be  made 
use  of  as  a  test  for  pyridine  bases  ;  it  depends  upon  the  formation 
of    alkylated    dihydro-pyridines,    e.g.  Dihydro-methyl-pyridine, 
C5H4.H2.N(CH3)  [Hofmann,  B.  14,  1497). 

Pyridine  is  polymerized  by  the  action  of  metallic  sodium  to  Dipyri- 
dine,  CioHjoNg  (an  oil,  B.  Pt.  286-290°),  with  the  simultaneous  production 
of  25-Dipyridyl,  CioHgNg,  =  C5H4N— (long  needles,  M.  Pt.  114°), 
a  compound  corresponding  to  diphenyl  (p.  438)  ;  both  of  these  yield 
iso-nicotinic  acid  upon  oxidation.  An  isomeric  m-Dipyridyl  has  also 
been  prepared,  which  gives  nicotinic  acid  when  oxidized. 

Pyridine  car*  be  brominated  but  not  nitrated ;  it  can  also  be  sulphur- 


(III.) 


N 


Pyridine. 


486 


XXXIII.  PYRIDINE  GROUP. 


ated,  with  the  formation  of  /3-pyridine-sulphonic  acid,  C5H4N.(S03H), 
from  which  potassium  cyanide  produces  Cyano-pyridine,  C5H4N.CN, 
and  fusion  with  potash  /3-oxy-pyridine. 

The  three  Oxy-pjnridines,  C5H4N"(OH)  (a-,  /3-,  7-),  are  best  prepared 
by  the  separation  of  COg  from  the  respective  oxy-pyridine-carboxylic 
acids,  a-  :  M.  Pt.  107°  ;  ^-  :  M.  Pt.  123°  ;  7-  :  M.  Pt.  148°.  They 
possess  the  character  of  phenols  and  are  coloured  red  or  yellow  by 
ferric  chloride.  As  in  the  case  of  phloroglucin,  so  here  also  there 
is  a  tertiary  as  well  as  a  secondary  form  to  be  taken  into  account, 
the  former  reminding  one  of  the  lactames  and  the  latter  of  the 
lactimes ;  for  instance,  7-oxy-pyridine  may  either  have  the  formula 

C2H2<^'^^'>C2H2  or  C2H2<^g>C2H2,  the  latter  of  the  two  repre- 

senting  a  keto-dihydro-pyridine  ('^  pyridone  ").  Both  of  the  methyl 
derivatives,  Methoxy-pyridine  and  Methyl-pyridone,  which  result  from 
these  two  forms  by  the  exchange  of  H  (of  the  OH  or  NH  respectively) 
for  CH3,  are  known  (B.  19,  19  ;  20,  956). 

Trioxy-pyridine,  C5H5NO3.  By  the  condensation  of  acetone-dicar- 
boxylic  ether  with  ammonia  there  is  produced  Glutazine,  C5HgN202 
(colourless  plates  soluble  in  alkali),  which  is  converted  by  boiling 
hydrochloric  acid  into  ammonia  and  trioxy-pyridine  (yellowish  micro- 
scopic prisms  or  needles).  For  its  constitution  see  B.  19,  2694 ;  20, 
2655.) 

Homdlogues  of  Pyridine. 

(Cf.  Ladenhurg,  A.  247,  1.) 

Methyl-pyridines  or  Picolines,  C5H4N(CH3).  All  the  three 
picolines  are  contained  in  bone  oil  and  probably  also  in  coal 
tar.  The  /3-compound  results  from  acrolein-ammonia  (p.  482) 
and  also  upon  heating  strychnine  with  lime.  They  are  liquids 
of  unpleasant  piercing  odour  resembling  that  of  pyridine,  and 
they  yield  a-,  /S-  or  7-  pyridine-carboxylic  acid  when  oxidized, 
a-:  B.  Pt.  120°;  ft-:  B.  Pt.  142-144°;  7-:  B.  Pt.  142-145°. 

Ethyl-pyridines,  CgH4N(C2H5),  are  also  known,  a-Ethyl-pyridine 
(B.  Pt.  148*5°)  being  obtained  by  the  breaking  up  of  tropine. 

Propyl-  and  Isopropyl  Pyridines,  C5H4N(C3H7),  have  been  carefully 
investigated  on  account  of  their  near  relation  to  conine.  They  are 
prepared  as  given  at  p.  483,  12.  Conyrine,  CgHjiN  (liquid,  B.  Pt. 
166-168°),  which  results  upon  heating  conine,  C8H17N,  with  zinc  dust, 
and  which  goes  into  conine  again  when  treated  with  hydriodic  acid,  is 
a-normal  propyl-pyridine. 


HOMOLOGUES  AND  OAKBOXYLIC  ACIDS  OF  PYRIDINE.  487 


a-Allyl-pyridine,  C5H4N(C3H5),  is  produced  when  a-picoline  is  heated 
with  aldehyde  : 

C5H4N.CH3  +  OHC-CH3  =  C5H4N.CH=CH— CH3  +  HgO. 

Reduction  transforms  it  into  inactive  conine  (B.  Pt.  189-190°). 

Dimethyl-pyridines  or  Lutidines,  C5H3N( 0113)2.  The  presence  of  the 
three  lutidines  has  been  proved  in  bone  oil  and  coal  tar.  For  their 
synthetical  formation  see  p.  483.  a-7-Lutidine  boils  at  157°,  and  the 
aa'-compound  at  142-143°. 

The  CoUidines,  CgH^iN,  are  isomeric  with  the  propyl-pyridines. 
Some  of  them  are  present  in  bone  oil  and  can  be  prepared  from  cin- 
chonine  by  distilling  the  latter  with  caustic  potash  (p.  482).  The 
collidine  {a-a'-y)  which  is  obtained  from  aceto-acetic  ether  and  aldehyde- 
ammonia  (p.  482),  boils  at  171-172°.  Aldehydine  "  (from  aldehyde, 
p.  482)  is  ^'-ethyl-a-methyl-pyridine  (B.  21,  294). 

a-  and  jS-Phenyl-pyridines,  C5H4N(C6H5),  are  analogous  to  diphenyl. 
(See  Monatsch.  f.  Chemie,  IV.,  456,  472.) 


Pyridine-carboxylic  acids, 
(See  Summary,  also  A.  241,  1.) 

The  Pyridine-mono-carboxylic  acids,  C5H4N(C02H),  result 
from  the  oxidation  of  all  the  pyridine  derivatives  which  con- 
tain only  one  (carbon-containing)  side-chain,  i.e.  from  methyl-, 
propyl-,  phenyl-,  etc.  pyridines;  also  from  the  pyridine-dicar- 
boxylic  acids  by  the  breaking  up  of  one  of  the  carboxyls,  just 
as  benzoic  acid  results  from  phthalic.  It  is  the  carboxyl  which 
stands  nearest  to  the  nitrogen  which  is  first  eliminated  here. 
Nicotinic  acid  is  also  produced  by  the  oxidation  of  nicotine. 
They  unite  in  themselves  the  characters  of  the  basic  pyridine 
and  of  an  acid,  and  are  therefore  comparable  with  glycocoll. 
They  yield  salts  with  HCl,  etc.  and  double  salts  with  HgCl2, 
PtCl4,  etc. ;  on  the  other  hand  they  also  form  salts  as  acids, 
those  with  copper  being  frequently  made  use  of  for  the  separa- 
tion of  the  acid. 

The  a-  acid  is  Picolinic  acid;  needles,  M.  Pt.  135°. 
The  /?-     „     Nicotinic  acid;  needles,  M.  Pt.  231°. 
The  y-     „     Iso-nicotinic  acid;  needles,  M.  Pt.  about  305°. 
It  is  noteworthy  that  the  a-  and  /3-acids  (and  also  e.g.  the  /3-7-dicarb- 


488 


XXXIII.  PYRIDINE  GROUP 


oxylic  acid)  readily  yield  up  their  nitrogen  as  ammonia  when  acted 
upon  by  sodium  amalgam,  being  thereby  transformed  into  unsaturated 
acids  of  the  fatty  series. 

Pyridine- dicarboxylic  acids^  C5H3N(C02H)2. 

a-jS-  =  Quinolinic  acid,  M.  Pt.  about  223°. 

a-7-  =  Lutidinic  acid,  M.  Pt.  235°. 

a-a'-  =  Dipicolinic  acidy  M.  Pt.  226°. 

a-j3'-  =  Iso-cinchomeronic  acid,  M.  Pt.  236°. 

/3-j3'-  =  Dinicotinic  acid,  M.  Pt.  over  285  . 

p.y.  =  Cinchomeronic  acidj  M.  Pt.  over  250°. 

Quinolinic  acid  (short  glancing  prisms),  the  analogue  of  phthalic  acid, 
results  from  the  oxidation  of  quinoline,  just  as  phthalic  acid  does  from 
naphthalene  ;  cinchomeronic  and  iso-cinchomeronic  acids  from  the  oxida- 
tion of  cinchonine  and  quinine.  The  constitution  a-jS-  follows  for 
quinolinic  acid  from  its  mode  of  formation  (p.  483). 

The  pyridine-mono-  and  di-carboxylic  acids,  which  contain  a  carboxyl 
in  the  a-position,  give  a  reddish-yellow  colouration  with  ferrous  sul- 
phate. 

Pyridine-tricarboxylic  acids,  C5H2N(C02H)3,  are  obtained  in  a  similar 
manner  by  the  oxidation  of  quinine,  cinchonine  (Carbo- cinchomeronic 
acid),  berberine  (Berberonic  acid),  etc. 

Pyridine-pentacarboxylic  acid  (from  coUidine-dicarboxylic  acid)  has 
no  longer  basic  properties  ;  it  readily  gives  up  COg. 

Hydro-derivatives  of  Pyridine, 

Piperidine,  C^H^^N  {Wertheim,  Bochleder,  1850),  is  a  colour- 
less liquid  of  peculiar  odour  slightly  resembling  that  of  pepper, 
and  strongly  basic  properties,  readily  soluble  in  water  and 
alcohol;  B.  Pt.  106°.    It  forms  crystalline  salts. 

It  occurs  in  pepper  in  combination  with  piperic  acid,  C12H10O4  (p.  427), 
in  the  form  of  the  alkaloid  Piperine,  CigHigNOg,  =  CgHjolS" — C12H9O3. 
i.e.  piperyl-piperidine,  which  crystallizes  in  prisms,  M.  Pt.  129°;  from 
this  latter  it  may  be  prepared  by  boiling  with  alkali. 

For  its  formation  from  pyridine  and  from  penta-methylene-diamine, 
see  p.  482. 

Piperidine  is  a  secondary  amine ;  its  imido-hydrogen  is  replaceable 
by  alkyl  and  by  acid  radicles. 

According  to  theory,  Di-  and  Tetra-hydro-pyridines  and  derivatives 
of  these  may  exist.  Tetrahydro-pyridine  derivatives,  **  Piperideins," 
e.g.  a-Pipecolein,  CgHiiN,  have  been  prepared  by  Ladenhurg,  by  the 
action  of  bromine  and  caustic  soda  upon  the  piperidines  (B.  20,  1645). 


PIPERIDINE;  CONINE. 


489 


The  homologues  of  piperidine  have  been  designated  by  Lademhurg 
Pipecolines,  C5HioN(CH3),  Lupetidines,  05119^(0113)2,  Oopellidines, 
Or,H3N(OH3)3,  etc.  The  most  interesting  among  them  are  the  a-,  /3- 
and  7-Propyl-  and  Isopropyl-piperidines,  OgHioNCOgHy),  on  account  of 
their  near  relation  to  conine. 

Conine,  dextro-rotatory  a-normal-propyl-piperidine^  CgH^^N, 
=  C5HjQN(C3H.jr),  is  the  poisonous  principle  of  hemlock 
(Conium  Maculatum).  It  is  a  colourless  dextro-rotatory- 
liquid  of  stupefying  odour,  slightly  soluble  in  water ;  M. 
Pt.  167-168°.  Hydriodic  acid  at  a  high  temperature 
reduces  it  to  normal  octane,  while  nitric  acid  oxidizes  it  to 
butyric  acid,  and  potassium  permanganate  to  picolinic  acid 
(hence  the  a-position). 

Ladenhurg  has  prepared  it  synthetically  by  reducing  a-allyl-pyridine 
in  alcoholic  solution  by  means  of  sodium  (B.  19,  2578)  : 

C5H4N(C3H5)  +  4H,  =  C^HioNiCsH,). 

In  this  reaction  there  is  first  formed  the  optically  inactive  a-normal- 
propyl-piperidine,  which  is  broken  up,  by  crystallization  of  the  tartrate, 
into  conine  (dextro-conine)  and  a  Itevo-conine  which  resembles  the  other 
closely.  The  relations  of  these  two  bases  to  one  another  and  to  the 
inactive  modification  are  the  same  as  that  of  dextro-  to  Isevo-tartaric 
acid  and  of  both  of  these  to  racemic  acid  (cf.  B.  19,  2584).  Analogous 
relations  hold  good  with  regard  to  the  ethyl-piperidines. 

a-,  jS-  and  7-Coniceins,  OsHigN,  are  peculiar  bases  which  result 
from  the  (indirect)  separation  of  hydrogen  from  conine.  Conydrine, 
O18H17NO,  an  oxy -derivative,  occurs  along  with  conine  in  hemlock ;  it 
crystallizes  in  plates,  M.  Pt.  120°,  B.  Pt.  240°. 

As  secondary  bases,  piperidine  and  conine  yield  in  the  first  instance 
tertiary  bases,  Methyl- piperidine  and  -conine,  upon  methylation,  e.g. 
CqRiqN{CB.^),  These  unite  further  with  methyl  iodide,  the  resulting 
ammonium  iodides  being  convertible  into  hydroxides;  the  latter  how- 
ever do  not  again  break  up  into  their  components  upon  distillation, 
but  yield  Dimethyl-plperidine,  05H9N(OH3)2  and  Dimetliyl-conine, 
C8Hi5N(OH3)2,  the  ring  being  broken  (see  B.  19,  2628).  If  these  in 
their  turn  are  made  to  combine  with  OII3I,  there  result  ammonium 
iodides  which  give  off  their  nitrogen  as  tri-methylamine  when  distilled 
with  alkali,  and  yield  the  hydrocarbons  Piperylene,  OgPIg,  and  Oonylene, 
CsHh  (p.  57),  respectively  {HofmaiiTi's  method  of  breaking  up  the 
piperidine  bases,  B.  16,  2058). 

Tropidine,  OgHigN,  an  o.ly  base  (B.  Pt.  162°),  is  related  to  conine ; 
it  results  from  the  action  of  concentrated  hydrochloric  acid  upon 


490 


XXXIII.  PYRIDINE  GROUP. 


tropine,  and  is  probably  a  derivative  of  a  tetrahydro -pyridine  (B.  16, 
1142). 

Tropine,  CgHj^NO,  is  obtained  by  decomposing  atropine  (see 
below).  It  is  a  base  crystallizing  in  plates ;  M.  Pt.  62°,  B.  Pt. 
229°.  Very  probably  it  is  an  Oxy-ethyl-methyl-tetrahydro-pyridine, 
C,U,.Il,.(G,Y[,OH.y—l^{CR,),  (B.  15,  1029;  20,  1647).  It 
reacts  with  methyl  iodide  in  the  same  way  as  piperidine  and 
Conine  do,  yielding  tropilidene,  CyHg  (p.  58). 

Atropine,  Hyoscyamine  and  Hyoscine  are  three  isomeric 
bases  of  the  formula  Cj^HggNOg,  which  can  be  respectively 
prepared  from  Atropa  Belladonna,  Datura  Strammonium  and 
Hyoscyamus  niger,  and  which  are  remarkable  for  their 
mydriatic  action  (power  of  dilating  the  pupil  of  the  eye). 
Baryta  water  breaks  up  atropine  into  tropic  acid  and  Tropine, 
CgHjgNO,  and  hyoscine  in  an  analogous  manner  into  tropic 
acid  and  the  isomer  of  tropine,  Pseudo-tropine.  Tropic  acid 
and  tropine  reunite  again  to  atropine  when  their  dilute  hydro- 
chloric acid  solutions  are  evaporated  together. 

If,  instead  of  tropic  acid  itself,  a  homologue  is  employed,  homologous 
bases,  the  '^Tropeines  "  are  obtained  ;  thus  mandelic  acid  yields  Homa- 
tropine,  CieHgiNOg,  which  exerts  like  atropine  a  mydriatic  action, 
although  a  less  lasting  one  {Ladenhurg,  A.  217,  82). 

Belladonnine,  which  likewise  occurs  in  Atropa  Belladonna, 
can  be  split  up  into  tropic  acid  and  Oxytropine,  CgH^j^NOg. 

An  Iso-tropine  results  from  the  distillation  of  benzoyl-ecgonine  (p. 
501). 

Nicotine,  CioH^^Ng,  =  CioHg(He)N2,  the  poisonous  con- 
stituent of  tobacco  and  the  tobacco  plant,  is  a  hexahydro- 
dipijridyl.  It  is  a  strong  diatomic  base,  oily,  readily  soluble 
in  water,  alcohol  and  ether,  and  of  a  stupefying  odour.  It 
can  be  distilled  unchanged  in  an  atmosphere  of  hydrogen,  but 
becomes  rapidly  brown  in  the  air;  B.  Pt.  about  250°. 

It  yields  Iso-dipyridyl,  CioHgNg  (p.  485),  by  the  separation  of 
hydrogen,  and  Di-piperidyl,  CioHgoNg,  by  taking  more  hydrogen  up. 
The  two  dipyridyls  [p-  and  ??i-),  which  are  known,  combine  with 
hydrogen  to  form  iso-nicotine  and  nicotidine,  bases  isomeric  with 
nicotine.    Permanganate  of  potash  oxidizes  nicotine  to  nicotinic  acid. 


QUINOLINE  AND  ACRIDINE  GROUPS.  491 

consequently  the  two  pyridine  residues  of  which  the  former  is  built  up 
are  in  the  /3-position  to  one  another. 


Appendix  :  Pyrone  Group ;  Ketines. 

The  hypothetical  substance    Pyrone,"  C2H2<^  q  ^CgHg,  would  be 

an  oxygenated  compound  of  ketonic  nature  nearly  related  to  pyridine. 
Although  not  known  itself,  derivatives  of  it  are,  e.g.  Chelidonic  acid, 
C7H4O6  (present  in  cellandine),  is  one  of  its  dicarboxylic  acids  ;  further, 
Meconic  acid,  C7H4O7  (present  in  opium),  P3n:omeconic  acid,  C6H4O5, 
which  can  be  prepared  from  the  latter,  and  Cumalic  acid,  C6H4O4, 
which  is  obtained  as  given  at  p.  239,  all  belong  to  this  group.  These 
compounds  are  of  especial  interest  because  they  are  readily  trans- 
formed into  pyridine  derivatives  by  ammonia,  e.g.  cumalic  acid  yields 
in  this  way  oxy -nicotinic  acid  (B.  17,  2384).  For  the  synthesis  of  com- 
pounds of  this  nature,  see  B.  19,  19 ;  20,  154. 

If  two  methine  groups  in  benzene  are  replaced  by  two  atoms  of 
nitrogen,  one  arrives  at  the  formula  : 

N 
N 

It  appears  as  if  the  so-called  Ketines  were  homologues  of  the  above 
hypothetical  substance  (which  is  termed  ^*Pyrazine"  or  "Aldine"), 
the  ketines  being  bases  obtained  by  the  reduction  of  isonitroso-acetone 
and  analogous  compounds  (see  p.  143;  B.  16,  3073;  19,  2526;  21, 
19). 


XXXIV.  THE  QUINOLINE  AND  AORIDINE 
GROUPS. 

A.  Quinoline  Group,  CnHgn-nN. 

The  quinoline  group  comprises  quinoline,  its  substitution 
products,  homologues,  carboxylic  acids,  etc.,  all  of  which 
remind  one  of  the  corresponding  compounds  of  the  pyridine 
group  in  their  behaviour  (cf.  Summary,  p.  480). 

Quinoline  stands  to  pyridine  as  naphthalene  does  to  benzene. 


492  XXXIV.  <;)UINOLINE  AND  ACRIDINE  GROUPS. 


Formation.  1.  By  the  dry  distillation  of  nitrogeneous 
organic  substances,  and  from  alkaloids  as  given  at  p.  481. 
Cinchonine  yields  quinoline  itself  when  heated  with  potash 
(Gerhardty  1842),  and  quinine  gives  methoxy-quinoline  (p.  496). 

2.  Quinoline  is  produced  when  aniline  is  heated  with 
glycerine  and  sulphuric  acid  in  presence  of  nitro-benzene 
(Skraup,  B.  14,  1002;  Monatsh.  f.  Chemie,  I.  316;  II.  141) : 

r  H  +  CH,(OH)-CH(OH)    .  ^  ^  ^  „  .CH=CH 

Aniline.  Glycerine.  Quinoline. 

The  nitro-benzene  simply  acts  as  an  oxidizing  agent ;  the  formation 
of  acrolein  as  intermediate  product  is  to  be  assumed  here,  the  latter 
combining  in  the  first  instance  with  aniline  to  acrolein-aniline.  The 
homologues  and  analogues  of  aniline  yield  homologues  and  analogues  of 
quinoline  by  corresponding  reactions  ;  when  naphthylamine  is  used,  the 
more  complicated  naphtho-quinolines  result  (see  below). 

3.  Quinoline  is  formed  by  the  separation  of  the  elements  of  water 
from  o-amido-cinnamic  aldehyde  (Baeyer  and  Drewson,  B.  16,  2207) : 

/CH-CH— CHO  XH=CH 

^  ^^NHg  '  N=CH  ' 

Carbostyril  (a-oxy-quinoline)  results  in  an  analogous  manner  from 
o-amido-cinnamic  acid  (Baeyer) : 

XH=CH  XH-CH 
'         NH2CO.OH  '  N=C.(OH)  ' 

Of  historical  interest  is  a  partly  analogous  synthesis  of  quinoline  by 
the  action  of  phosphorus  pentachloride  upon  hydro-carbostyril  (p.  417), 
and  reduction  of  the  resulting  dichloro-quinoline,  C9H5NOI2,  by  means 
of  hydriodic  acid  {Baeyer,  B.  12,  1320). 

4.  When  aniline  is  heated  with  aldehyde  (para-aldehyde) 
and  hydrochloric  acid,  a-methyl-quinoline  (quinaldine)  is 
obtained  (Doebner  and  v.  Miller) : 

CeH^-NH,  +  2C2H4O  +  0  =  CioH,N  +  SH^O. 
In  this  reaction  aldol  is  formed  as  intermediate  product,  thus : 
OHC--CH2  ^     ^  .CH=CH 

Aniline.  Aldol.  Quinaldine. 


FORMATION  OF  QUINOLINE  DERIVATIVES. 


493 


Here,  again,  various  other  primary  aromatic  amines  may  be  used 
instead  of  aniline;  and  other  aldehydes  (B.  18,  3361)  or  ketones  [e.g. 
B.  19,  1394)  instead  of  para-aldehyde. 

5.  Aniline  and  aceto-acetic  acid  combine  together  at  temperatures 
above  110°  to  aceto-acetanilide,  CHg — CO — CHg — CO.NH.CgHg,  from 
which  7-methyl-a-oxyquinoline  (*' methyl-carbostyril "  or  "a-oxy-7- 
lepidine")  results  on  the  elimination  of  water  {Knorr,  A.  2  36,  75) : 

CH3  CH3 

Aceto-acetanilide.  7-Methyl-carbostyril. 

Aniline  can  also  react  with  aceto-acetic  ether  (under  100°),  with  the 
formation  of  jS-Phenyl-amido-crotonic  ether, 

CgHg— NH— C(CH3)=CH— CO2C2H5,  which  yields  v-oxy-quinaldine 
when  heated  {Conrad  and  Limpach,  B.  20,  944) : 

•   ^  ^  /C(OH)-CH 
CeH,     CO-CH         =   CeH<  '  +  C.Hfi, 

^NH— C-CH3  ' 

Analogously  to  aceto-acetic  ether  (which  is  the  ether  of  a  jS-ketonic 
acid),  the  jS-diketones  likewise  -condense  with  aniline ;  further,  also, 
mixtures  of  ketones  and  aldehydes,  or  mixtures  of  aldehydes  which 
would  yield  /3-diketones  or  j8-ketonic  aldehydes  if  condensed  together 
(C,  Beyer f  B.  20,  1767).  With  acetyl-acetone  we  obtain  (e.g.)  a-y- 
dimethyl-quinoline : 

CO-CH3  ~"  '"^N^C-CHg 

These  reactions  are  nearly  allied  to  those  already  spoken  of  under  4. 

6.  o-Amido-benzaldehyde  undergoes  condensation  with  aldehydes 
and  ketones  under  the  influence  of  dilute  caustic  soda  solution,  with 
the  formation  of  quinoline  derivatives  {Friedldnder,  B.  15,  2574;  16, 
1833).  With  aldehyde  quinoline  itself  results,  and  with  acetone 
quinaldine : 

C6H4(NH2).CHO  +  CsHgO  =  C10H9N  +  211^0; 
or,  generally  : 

XHO      CHo— R  .CH=C— R 

^  ^^NH^       CO-ir  ^  ^  N=C— R'  ' 

Acetophenone,  aceto-acetic  ether  and  malonic  ether  also  react  in  a 
similar  way. 


4:94  XXXIV.  QUINOLINE  AND  ACRIDINE  GROUPS. 


7.  Quinoline  is  produced  when  the  vapour  of  allyl-aniline  is  led  over 
heated  oxide  of  lead  {Konigs)  ; 

8.  Also  by  oxidizing  acridine  to  acridinic  acid,  C9H5N(C02H)2  (p. 
497),  and  eliminating  the  carboxyls. 

9.  For  further  syntheses  see  B.  18,  632,  1460,  2632,  2975. 

Constitution.  The  above  modes  of  formation  (especially  3 
and  5)  show  that  quinoline  is  an  ortho-di-derivative  of 
benzene,  and  that  it  contains  its  nitrogen  linked  directly  to 
the  benzene  nucleus ;  they  also  show  that  the  three  C-atoms, 
which  enter  the  complex,  form  a  new  hexagon  (pyridine)  ring 
with  this  nitrogen  and  with  two  carbon  atoms  of  the  benzene 
ring.  The  latter  point  also  follows  from  the  oxidation  of 
quinoline  to  pyridine-dicarboxylic  acid  (Hoogewerff  and  van 
Dorp) : 

CO2H— CH— CH=CH 
CO2H— CH—  N  =CH 
Quinolinic  acid. 

We  have  thus  the  following  constitutional  formula : 
CH  CH 


^  _  XH=CH 
N=CH 
Quinoline. 


0, 


+    2CO2    +  HnO. 


HC 


HC 


CH 


CH 


HC 


N 


The  second  of  these  two  modes  of  writing  the  formula  possesses  this 
advantage  over  the  first  that  it  is  independent  of  special  assumptions 
with  regard  to  the  mode  in  which  each  fourth  carbon-  or  third  nitrogen- 
affinity  is  taken  up.  One  may  also  assume  here  a  mode  of  linking 
corresponding  to  that  of  the  pyridine  formula  III.  (p.  485). 

Quinoline  is  thus  constituted  in  a  manner  perfectly  analogous 
to  naphthalene,  and  may  be  looked  upon  as  being  derived  from 
the  latter  by  the  exchange  of  CH  for  N,  or  by  the  condensa- 
tion   of  a  pyridine  and  a  benzene  nucleus. 

When  quinoline  derivatives  are  oxidized,  the  benzene  residue  usually 
proves  itself  to  be  less  stable  than  the  pyridine  one.  This  is  shown  in 
the  case  of  quinoline  itself,  the  benzene  nucleus  being  destroyed  upon 
its  oxidation  to  pyridine-dicarboxylic  acid  (p.  488).  a-Methyl-quinoline 
gives,  on  the  other  hand,  acetyl-o-amido-benzoic  acid  when  oxidized  : 


CONSTITUTION  OF  QUINOLINE. 


495 


C6H4< 


,CH-CH 


+  0,  =  C,H,<. 


CO.OH 
NH— CO.CH. 


3 


+  CO. 


The  pyridine  nucleus  of  quinoline  takes  up  hydrogen  more  readily 
than  the  benzene  one ;  thus  quinoline  is  easily  converted  (even  by  tin 
and  hydrochloric  acid)  into  tetrahydro-quinoline,  although  it  can  be 
reduced  further  only  with  difficulty. 

The  three  H-atoms  of  the  pyridine  nucleus,  counting  from 
the  N,  are  designated  as  a-,  P-  and  y-,  and  the  four  H-atoms 
of  the  benzene  nucleus  as  o-,  m-,  p-  and  a-  (ana-)  hydrogen 
atoms;  or  the  former  as  Py- 1,1  and  3,  and  the  latter  as  B-1, 
-2,  -3  and  4  atoms  {BaeyeVy  B.  17,  960).  Since  no  one  of  these 
H-atoms  is  linked  symmetrically  to  another,  seven  mono-deriv- 
atives of  quinoline  are  in  each  case  theoretically  possible.  As 
a  matter  of  fact  all  seven  quinoline-monocarboxylic  acids  have 
been  prepared. 

The  position  of  the  substituents  follows  :  {a)  from  the  nature  of  the 
products  which  result  upon  oxidation,  e.g.  B-quinoline-carboxylic  acid 
{i.e.  one  whose  carboxyl  is  linked  to  the  benzene  nucleus)  yields  a 
pyridine-dicarboxylic  acid,  while  a  Py-quinoline-carboxylic  acid  (whose 
carboxyl  is  linked  to  the  pyridine  nucleus)  yields  a  pyridine- tricar- 
boxylic acid ;  {b)  from  the  synthesis  of  the  compound  in  question. 
The  methyl-quinoline,  for  instance,  which  results  from  o-toluidine  by 
the  Skraup  synthesis  must  be  a  B-1 -compound  : 


whilst  m-toluidine  must  yield  aB-2-orB-4-,  and  ^-toluidine  aB-3-methyl- 
quinoline  (a    tolu-quinoline  "). 


Quinoline,  leucoUne,  C^H^N  {Runge^  1834),  is  also  found  in 
Idrian  ^^Stupp"  fat  (see  p.  477).  It  is  a  colourless  strongly 
refracting  liquid  of  a  peculiar  and  very  characteristic  odour; 
B.  Pt.  236°.  Quinoline  is  a  monatomic  base.  It  forms  a 
difficultly  soluble  bichromate,  (C9H^N)2,  CrgO^Hg.  Is  used  as 
an  antifebrile. 


Quinoline. 


496  XXXIV.  QUINOLINE  AND  ACRIDINE  GROUPS. 


Nascent  hydrogen  transforms  it  first  into  Dihydro  -  quinoline, 
C9H9N  (M.  Pt.  161°),  and  then  into  Tetrahydro- quinoline,  CgH^N, 

=  ^6H4<^jj  (liquid,  B.  Pt.  245°).    Since  both  of  these  yield 

nitrosamines  and  can  be  alkylated,  they  are  secondary  bases.  The 
tetrahydro-compound  exerts  a  stronger  antifebrile  action  than  the 
mother  substance,  especially  in  the  form  of  its  ethyl-derivative, 
Cairolin  (B.  16,  739). 

When  quinoline  is  heated  vi^ith  sodium,  a  Diquinolyline,  CgHgN-CgHgN, 
analogous  to  diphenyl  or  dipyridine,  is  formed ;  it  crystallizes  in  small 
plates  or  needles.  Quinoline  also  yields  Diquinoline,  (C9H7N)2  (yellow 
needles),  by  polymerizing. 

Halogen  derivatives  of  quinoline  and  nitro-quinolines  have  been 
prepared  by  the  Skrmip  reaction,  etc.  ;  and,  from  the  reduction  of  the 
latter,  amido-quinolines,  C9HgN(NH2).  The  quinoline-sulphonic  acids 
yield  cyano-quinolines  when  heated  with  potassium  cyanide,  and  oxy- 
quinolines  when  fused  with  potash.  Certain  of  the  last-named  com- 
pounds likewise  result  from  the  amido-phenols  by  the  Skrauj)  reaction, 
these  containing  the  hydroxyl  in  the  benzene  nucleus.  p-Methoxy- 
quinoline,  C9HgN(O.CH3),  is  the  anisol  of  the  quinoline  series  and 
resembles  quinoline  closely.  For  its  formation  from  quinine,  see  p. 
492. 

a-Oxy-quinoline,  carbostyril,  CgH4(C3H2N.OH),  is  a  quinoline 
hydroxylated  in  the  pyridine  nucleus  (see  p.  492,  mode  of 
formation  3).  It  crystallizes  in  white  needles  and  is  soluble 
in  alkali,  from  which  it  is  again  thrown  down  by  carbonic 
acid;  M.  Pt.  198-199°.  Its  constitution  follows  from  its 
formation  from  (?-amido-cinnamic  acid  (p.  492). 


Homologues  of  Quinoline;  condensed  Quinolines. 

Quinaldine,  a-methyl-quinoline,  O^^qHqN,  is  contained  in  coal 
tar.  It  is  a  colourless  liquid  of  quinoline  odour,  which  boils 
at  138°,  and  whose  oxidation  yields  either  a  benzene  or  a 
quinoline  derivative,  according  to  the  nature  of  the  oxidizing 
agent  (see  p.  494). 

The  hydrogen  of  the  methyl  group  readily  enters  into  reaction ; 
quinaldine  reacts  with  phthalic  anhydride  to  produce  a  beautiful  yellow 
dye,  Quinoline-yellow,  CioH7N(CO)2C6H4  (B.  16,  2602).  In  presence 
of  quinoline  quinaldine  is  transformed  into  the  (unstable)  blue  dyes,  the 
Cyanines,  when  alkylated  and  treated  with  caustic  potash. 


HOMOLOGUES  OF  QUINOLTNE,  ETC. 


497 


7-Methyl-quinoline,  lepidine,  cincho-Upidine^  Ci)HgN(CHo),  is  obtained 
by  distilling  cinchonine  with  oxide  oilead  ;  B.  Pt.  264°. 

The  methyl-quinolines  are  isomeric  with  the  naphthylamines.  The 
homologiies  of  quinoline  which  have  been  isolated  from  coal  tar  and 
bone  oil  are  known  as  Lepidine  or  Iridoline,  CjoH^N,  Cryptidine, 
CiiHiiN,  etc. 

Tetramethyl-quinoline,  M.  Pt.  64°,  B.  Pt.  284°  (B.  19,  1394). 
Phenyl- quinoline,  CgHeN— CgHg.  Py-3-phenyl-quinoline, 

C6H4<^         ^  is  to  be  regarded  as  the  mother  substance  of  the 

cinchona  alkaloids  {Konigs  and  iVe/,  B.  10,  2427). 

Flavaniline,  C16H14N2,  a  beautiful  yellow  dye,  which  results  upon 
heating  acetanilide  with  zinc  chloride,  is  an  a-amido-phenyl-7-methyl- 
quinoline  (B.  15,  1500). 

Naphtho-quinolines,  C13H9N.  These  compounds  (solid  bases),  which 
are  derived  from  phenanthrene  by  the  exchange  of  CH  for  N,  are 
obtained  by  subjecting  the  two  naphthylamines  to  the  Skraup  reaction. 
They  are  isomeric  with  acridine  (p.  498). 

Anthr a- quinoline,  CiyH^gN,  is  formed  in  an  analogous  manner  from 
anthramine  (p.  473).  It  crystallizes  in  colourless  plates  and  is  the 
mother  substance  of  alizarin  blue  (p.  475). 


QuiiwUne-carloxylic  Acids, 

All  the  seven  mono-carboxylic  acids  of  quinoline,  which  are  possible 
according  to  theory,  are  known.  Quinoline-benz-carboxylic  acids  are 
those  which  contain  the  carboxyl  group  in  the  benzene  nucleus. 

Cinchoninlc  acid,  CgHgNlCOgH),  which  results  from  the  oxidation  of 
cinchonine  by  permanganate  of  potash  and  crystallizes  in  needles  or 
prisms,  M.  Pt.  254°,  is  7-quinoline-carboxylic  acid.  From  it  is  derived 
V  7 

Quininic  acid,  C9H5N(OCH3).C02H,  which  is  obtained  by  oxidizing 
quinine  with  chromic  acid  ;  it  forms  yellow  prisms,  M.  Pt.  280°. 

a-/3-Qulnoline-dicart>oxylic  acid  or  acridinic  acid,  results  from  the 
oxidation  of  acridine. 


Bases  related  to  Quinoline, 

Iso-quinoline,  an  isomer  of  quinoline,  occurs  along  with  the  latter  in 
coal  tar  (B.  18,  Ref.  384).    It  is  a  solid ;  M.  Pt.  20-22°,  B.  Pt.  240  5°. 
Since  oxidation  converts  it  into  cinchomeronic  acid  (j8-7-Py-dicarboxylic 
(506)  21 


498  XXXIV.  QUINOLINE  AND  ACRIDINE  GROUPS. 


acid)  on  the  one  hand  and  phthalic  acid  on  the  other,  it  possesses  the 
constitution  :  |       I      tst-  synthesis,  see  B.  19,  1653,  2354. 


Basee  related  to  quinoline,  which  contain  in  the  molecule  two  atoms 
of  N  instead  of  (CH)  and  N,  and  which  have  the  formula  C6H4(C2H2N2), 
have  recently  been  prepared  in  considerable  number,  either  themselves 
or  in  the  form  of  derivatives  ;  among  these  are  the  Cinnoline-^  Quinazole- 
etc.  compounds  and  the  QuiiioxalineSy  (B.  16,  677;  17,  319,  724;  19, 
1604 ;  20,  Ref.  630). 

Quinoxaline  or  quinazine,  CqH^<C^       •    ,  results  from  the  action  of 

^  =011 

glyoxal  upon  o-phenylamine-diamine.  In  a  similar  manner  o-diamines 
combine  with  aldehyde  acids,  di-ketones,  ketonic  acids,  etc.,  if  these 
latter  contain  two  neighbouring  CO-groups  (see,  e.g.  B.  18,  1228; 
also  under  phenazine,  p.  501).    Quinoxaline  is  a  chromogene. 


B.  The  Acridine  Group,  O^Hg^.i^N. 

Acridine,  (Graebe  and  Caro),  is  a  base  crystallizing 

in  colourless  needles  and  capable  of  being  sublimed,  which  is 
present  in  the  crude  anthracene  of  coal  tar,  and  also  in  crude 
diphenylamine.  It  is  characterized  by  an  intensely  irritating 
action  upon  the  epidermis  and  the  mucous  membrane,  and 
also  by  the  greenish-blue  fluorescence  shown  by  dilute  solutions 
of  its  salts. 

It  is  prepared  synthetically  by  heating  diphenylamine  and  formic 
acid,  or  formyl-diphenylamine,  (C6ll5)2N.  CHO,  with  zinc  chloride 
{Bernthsen,  A.  224,  1),  and  is  also  obtained  when  the  vapour  of 
o-tolyl-aniline  is  passed  through  a  red-hot  tube.  Oxidation  converts 
it  into  a-j8-quinoline-dicarboxylic  acid  (p.  497) ;  its  formation  and 
constitution  are  thus  shown  by  the  following  equation : 

Formyl-diphenylamine.  Acridine. 

It  consequently  appears  as  an  anthracene  in  which  the  middle  group 
CH  is  replaced  by  N.    Acridine  is  a  tertiary  base. 

Methyl-  and  Butyl-acridines,  Phenyl-acridine,  C6H4<Cj;j-  ^C6H4, 

and  Naphtho-acridines  (i.e.  acridines  which  contain  CioHg  instead  of 
C(;H4),  have  all  been  prepared  synthetically  in  an  analogous  manner. 


OPIUM  BASES. 


499 


Methyl-acridine  can  be  oxidized  indirectly  to  Acridyl- aldehyde, 
CigHgN— CHO,  and  Acridine-carboxylic  acid,  CigHgN— CO2H  (B.  20, 
1541).  The  latter  compound  crystallizes  in  yellow  needles  and  is  at 
the  same  time  base  and  acid. 

The  Chrysaniline  or  pJiosphin  of  commerce,  a  beautiful  yellow  dye, 
is  diamido -phenyl- acridine,  Ci(jH^iN(N  112)2,  since  it  yields  phenyl- 
acridine  when  its  diazo-compound  is  boiled  with  alcohol. 

Acridine  is  therefore,  like  anthracene,  a  chromogene  (see  p.  24). 


0.  Alkaloids  of  unknown  Constitution. 

Some  of  the  alkaloids  which  occur  in  nature  are  free  from 
oxygen,  liquid,  and  volatile  without  decomposition;  while 
others  contain  oxygen,  are  (usually)  solid  and  crystalline,  and 
are  not  volatile  without  decomposition  (strychnine  volatilizes 
in  a  vacuum).  They  are  precipitated  by  certain  reagents  such 
as  tannic  acid,  phospho-molybdic  acid,  platinic  chloride,  the 
double  iodide  of  mercury  and  potassium,  potassic  iodide,  etc. 
Many  of  them  give  intensive  colour  reactions  with  nitric  acid, 
chlorine  water,  concentrated  sulphuric  acid,  etc. 

{a)  Opium  bases. 

Opium  (Papaver  somniferum)  contains  : 

1.  Morphine,  Ci^HigNOg,  =  Ci^Hi^N0(0H)2,  a  monatomic 
and  tertiary  base.  It  crystallizes  in  small  prisms  (  +  HgO)  of 
bitter  taste,  and  is  a  valuable  soporific. 

When  distilled  with  zinc  dust  it  yields  phenanthrene  in  addition  to 
pyrrol,  pyridine  and  quinoline,  and  it  is  also  convertible  into  phenan- 
threne derivatives  in  another  way  (A.  2  22,  235).  Its  molecule  may 
therefore  contain  a  phenanthrene  ring  together  with  a  pyridine  ring 
made  up  of  the  remaining  three  carbon  and  one  nitrogen  atoms,  and  the 
two  neighbouring  carbon  atoms  of  the  phenanthrene. 

2.  Codeine,  methyl-morphine,  CigHgiNOs,  can  be  prepared  by  methy- 
lating  morphine. 

3.  Thebaine,  CigHgiNOg;  4.  Papaverine,  C21H21NO4;  5.  Narceine, 
6.  Narcotine,  CggHggNO^,  crystallizes  in  glancing  prisms. 


500         XXXIV.  QUINOLINE  AND  ACRIDINE  GROUPS. 


It  is  decomposed  by  the  action  of  water  into  Meconine, 
C^qH^qO^  (cf.  p.  430),  also  present  in  opium,  and  Cotarnine, 
CjgH^gNOg  (prisms,  +  H^O),  which  latter  is  convertible  by 
bromine  into  dibromo-pyridine. 

(b)  Cinchona  bases. 

Quinine  barks  (i.e.  the  Cinchona  varieties)  contain : 

1.  Quinine,  CgoHg^NgOg  +  SHgO,  a  diatomic  base  of  intensely 
bitter  taste  and  alkaline  reaction,  whose  sulphate  and  chloride 
are  universally  used  as  febrifuges.  It  crystallizes  in  prisms  or 
silky  glancing  needles;  M.  Pt.  177°.  The  quinine  salts  in 
dilute  solution  are  characterized  by  a  magnificent  blue  fluor- 
escence. 

As  a  base  quinine  is  a  tertiary  diamine,  but  it  contains  in  addition — 
as  its  reactions  show — a  hydroxyl  and  a  methoxyl,  and  seems  to  be  a 
derivative  of  a  partially  hydrogenized  di-quinoline,  corresponding  with 
the  formula  ; 

C9He(OCH3)N-C9Hn(OH)N.CH3. 

It  yields  quininic  acid,  C9H5N(OCH3)C02H  (p.  497),  upon  oxidation, 
and  methoxy-quinoline,  CgHgNlOCHs),  when  fused  with  potash.  (Cf. 
p.  496;  B.  14,  1852;  A.  204,  90.) 

When  quinine  is  warmed  with  hydrochloric  acid  to  140-150°,  CHg 
is  separated  and  Apo-CLUinine,  0191122^20,  =  CigHgoNglOHja,  formed. 

2.  Cinclionine,  C19H22N2O,  =  Ci9H2iN2(OH),  is  derived  from  quinine 
by  the  exchange  of  (OCH3)  for  H.  It  forms  white  sublimable  prisms  or 
needles,  is  a  weaker  febrifuge  than  quinine,  and  yields  cinchoninic  acid 
upon  oxidation  and  quinoiine  on  fusion  with  potash. 

3.  Conchinine,  C20H24N2O2,  and  4.  Cinchonidine,  C19H22N2O,  are 
isomeric  with  quinine  and  cinchonine  respectively,  and  milder  in  their 
action, 

(c)  Strychnine  bases, 

Strychnos  nux  vomica  and  certain  other  beans,  etc.  con- 
tain : 

I.  Strychnine,  C21H22N2O2,  and  2.  Brucine,  023112(3X204. 
The  former,  which  is  excessively  poisonous  (producing  tetanic 


STRYCHNINE  ;  COCAINE  ;  THE  AZINES. 


501 


spasms),  crystallizes  in  four-sided  prisms  and  yields  quinoline 
and  indole  when  fused  with  potash,  and  ^-picoline,  etc.,  when 
distilled  with  lime.  Brucine  (prisms)  is  converted  into  homo- 
logues  of  pyridine  on  fusion  with  potash. 

(d)  Solanine  bases,  see  Atropine,  p.  490. 

Among  other  alkaloids  may  be  mentioned  : 
Veratrine,  C22H42N'09,  from  Veratrum  album. 

Sinapine,  CjsHgsNOg,  is  a  derivative— not  of  pyridine — but  of  choline 
on  the  one  hand  and  of  gallic  acid  on  the  other. 
Sparteine,  C15H26N2  (in  Spartium  Scoparium). 

Cocaine,  Ci^H2iN04,  is  the  active  constituent  of  the  coca- 
leaf  (Erythroxylon  Coca).  It  crystallizes  in  colourless  prisms 
and  is  a  powerful  anaesthetic.  For  its  constitution,  see  B.  20, 
1121;  21,  47. 

Hydrochloric  acid  breaks  it  up  into  benzoic  acid,  Ecgonine,  C9H15NO3 
(prisms),  and  methyl  alcohol,  and  it  may  be  conversely  reproduced  by 
benzoating  ecgonine  and  then  methylating  the  resulting  benzoyl- 
ecgonine. 

For  the  alkaloids  produced  by  the  decomposition  of  dead 
bodies,  which  are  termed  Ptomaines,  see  p.  516. 


D.  Phenazine  group  (the  Azines), 

As  phenazine  or  azo-phenylene  is  designated  a  compound, 
CjgHgNg,  which  corresponds  to  anthracene  and  acridine  in 
constitution,  since  it  contains  two  benzene  residues  connected 
by  two  N-atoms  which  are  also  linked  to  one  another ;  thus : 

This  compound  is  of  great  interest  because,  like  anthracene 
and  acridine,  it  possesses  the  chromogenic  character,  being 
converted  into  dyes  by  the  entrance  of  amido-groups. 

Phenazine  results  from  the  distillation  of  barium  azo-benzoate,  upon 


502  XXXIV.  QUINOLINE  AND  ACRIDINE  GROUPS. 


leading  the  vapour  of  aniline  through  red-hot  tubes,  and  by  the  oxida- 
tion of  its  hydro-compound  (see  below).  It  crystallizes  in  beautiful 
long  bright  yellow  needles,  M.  Pt.  171°,  which  can  be  readily  sub- 
limed, is  only  sparingly  soluble  in  alcohol  but  easily  in  ether,  and 
soluble  in  concentrated  sulphuric  acid  with  a  red  colour  ;  the  alcoholic 
solution  yields  a  green  precipitate  on  the  addition  of  stannous  chloride. 
When  reduced  with  sulphide  of  ammonium  it  goes  into  a  colourless 

hydro-compound,  Hydro-phenazine,  C6H4<^-^jj^C6H4  (readily  oxidiz- 

able  plates).  This  latter  is  also  formed  synthetically  by  heating  pyro- 
catechin  with  o-phenylene-diamine  (B.  19,  2206)  : 

C6H4<^Q^  +  iJh!^^6^4     =     C6H4<;!^^>C6H4  +  2H2O. 

Among  the  analogues  of  phenazine  is  Naphthazine  (see  naphtho- 
acridine),  which  contains  two  naphthalene  residues  linked  together  by 

When  one  amido-group  substitutes  in  such  azines,"  there 
are  formed  the  Eurhodines  (B.  19,  441),  sublimable  dyes  of  a 
colour  varying  from  j^ellow  to  red ;  and  when  two  amido- 
groups,  the  dyes  of  the  toluylene  red  group. 


Toluylene  red. 

Toluylene  red,  C15H16N4  (  Witt) .  When  jp-amido-dimethyl-aniline  is 
oxidized  in  the  cold  along  with  m-toluylene-diamine,  the  beautiful  blue 
compound  Toluylene  blue,  an  indamine  (p.  356),  results,  which  gives  up 
hydrogen  and  goes  into  toluylene  red  when  boiled  : 

nh/ 

Amido-dimethyl-aniline.  Toluylene-diamine. 

=  (CH3)2N-C,H3<|>CeH,(CH3)-NH2  +  SH^O. 
Toluylene  red. 

Other  similar  compounds  can  be  prepared  in  an  analogous  manner. 
The  simplest  toluylene  red,  which  results  from  29-phenylene-diamine  and 
m-toluylene-diamine  and  which  contains  NHg  in  place  of  N(CH3)2, 
yields  Methyl-phenazine,  CgH4{N2}C6H3(CH3),  when  diazotized  ;  it  con- 
tains therefore  two  primary  amido-groups. 

Toluylene  red  is  used  on  the  technical  scale  as  "  Neutral  red." 


PHENO-  AND  TOLU-SAFRANINES,  ETC. 


503 


Safranines, 

The  Safranines  are  related  to  toluylene  red.  They  are 
produced  by  oxidizing  an  aqueous  solution  of  a  mixture  of 
the  sulphates  of  ^-phenylene-di amine  (1  mol.)  with  a  primary 
monamine  (1  mol.)  and  a  second  monamine  in  which  the 
^-position  is  unoccupied  (1  mol.).  The  simplest  safranine  is 
Pheno-safranine,  CigHi^N^Cl  [from  CeH4(NH2)2  + SCoH^.NHJ, 
while  the  ordinary  safranine  of  commerce  consists  principally 
of  Tolu-safranine,  C^iH^oN^  [from  C6H3(CH3)(NH2)2  (1:2:4) 
and  2C6H4(CH3)NH2].  See  B.  16,  472,  etc.  The  requisite 
mixture  of  mono-  and  diamines  is  attained  in  practical  working 
by  the  reduction  of  amido-azo-compounds  (see  p.  370). 

The  safranines  are  beautiful  crystalline  compounds  of  a 
metallic  green  glance,  readily  soluble  in  water,  which  dye 
yellowish-red  to  red.  The  solution  in  concentrated  sulphuric 
acid  is  green,  becoming  blue,  violet,  and  finally  red  on  dilution 
with  water.  Eeduction  gives  rise  to  leuco-compounds,  which 
are  probably  diamido-compounds  of  the  as  yet  unknown  sub- 
stance C6H4<JJ^^  jj  ^>C6H4(B.  20,  2690,  3017,  3121,  etc.). 

Mauveine,  C27H25N4CI,  the  first  aniline  dye  which  was  prepared  on 
the  technical  scale  (by  PerTcin  in  1856,  from  crude  aniline,  bichromate 
of  potash   and  sulphuric  acid),  is  possibly  phenylated  safranine, 

Magdala  red,  C30H21N4CI,  is  the  safranine  of  the  naphthalene  series. 
Appendix.    Dyes  of  unknown  Constitution, 

The  Indulines  and  Nigrosines  are  violet-blue  to  grey-blue  dyes  which 
result  upon  heating  the  amido-azo-benzenes  with  the  aniline  hydro- 
chlorides, and  sulphurating  the  product  so  obtained.    They  are  derived 
from  Violaniline  or  azo-diphenyl  blue,  CigHisXs  ' 
CeHg-N^N-C^H^.NH^  -^  C.Hg.NH^,  HCl  =  CisHi^Ng  +  NH^Cl, 

which  latter  compound  also  results  (in  place  of  fuchsine)  from  the 
oxidation  of  chemically  pure  aniline,  (cf.  p.  351). 

Aniline  black,  (C30H27N5?),  obtained  by  acting  upon  aniline  with  {e.g.) 
KCIO3  in  the  presence  of  copper  or  vanadium  salts,  is  usually  produced 
directly  upon  the  fibre  ;  it  is  a  dark  green  amorphous  powder,  insoluble 
in  most  menstrua. 


504 


XXXV.  TERPENES  AND  CAMPHORS. 


XXXV.  TERPENES  AND  CAMPHORS. 

The  terpenes  are  hydrocarbons  of  the  formula  G^oH^g  [or 
(C5H8)J,  which  are  nearly  related  to  cymene  (p.  331).  The 
camphors,  e.g.  common  Camphor,  C^oH^gO,  contain  oxygen  in 
addition,  but  are  closely  allied  to  the  terpenes.  Both  classes 
of  compounds  are  widely  distributed  in  nature. 

Ethereal  oils.  Many  plants  contain,  especially  in  their  blossoms 
and  fruits,  oily  substances  to  which  they  owe  their  peculiar  fragrance 
or  odour,  and  which  can  be  obtained  from  them  e.g.  by  distillation  with 
steam.  These,  which  are  termed  ethereal  oils,  were  formerly  grouped 
together  in  a  special  class,  but  now  they  are  recognized  as  being 
more  or  less  heterogeneous ;  thus  oil  of  bitter  almonds  is  benzoic 
aldehyde,  and  Ivoman  oil  of  cumin  is  a  mixture  of  cymene  and 
cumic  aldehyde,  etc.  Many  of  these  ethereal  oils  contain  terpenes, 
e.g.  oil  of  thyme  consists  of  thymene  (a  terpene)  together  with  cymene 
and  cumene  ;  in  fact  the  terpenes  are  often  their  chief  constituents,  as 
in  the  case  of  turpentine,  citron  and  orange  oils,  etc.  Many  oils 
deposit  solid  substances,  the  "  stearoptenes,"  when  exposed  to  cold, 
the  liquid  portions  being  termed  "Elseoptenes."  The  camphor  varieties 
resemble  the  ethereal  oils  in  their  occurrence  and  modes  of  preparation, 
but  they  are  solid. 

A.  Terpenes. 

The  terpenes  are  nearly  related  to  cymene,  C^qH^^  ;  thus  oil 
of  turpentine  goes  directly  into  cymene  when  heated  with 
iodine.  They  yield  terephthalic  acid,  CgH4(C02H)2,  upon 
oxidation,  and  are  therefore  to  be  regarded  as  di-hydrides  of 
cymene,  C^QH^^.Hg  (see  p.  331). 

A  peculiar  reaction  of  the  terpenes  consists  in  their  capacity  for  com- 
bining with  hydrochloric  acid  to  form  either  mono-hydrochlorides, 
CioHiyCl  (in  the  case  of  the  pinenes  or  camphenes),  or  di-hydrochlorides, 
CioHigClg ;  the  same  applies  to  hydrobromic  and  hydriodic  acids. 
They  also  unite  with  bromine,  often  to  characteristic  tetrabromides, 
CioH^gBr4,  and  also  in  part  with  water  (see  terpin  hydrate),  and  with 
nitrogen  trioxide.  The  combination  with  halogen  hydride  is  readily 
effected  in  an  acetic  acid  solution  saturated  with  the  gas,  and  that  with 
bromine  by  using  warm  acetic  ether  as  the  diluent.  When  the  solution 
of  the  halogen  hydride  addition  product  is  heated  with  sodium  acetate, 
the  halogen  acid  is  split  off. 


THE  TERPENES. 


505 


The  terpenes  polymerize  readily  and  show  great  inclination  to  change 
into  isomers  under  certain  conditions.  Their  solution  in  acetic  anhyd- 
ride gives  a  yellow,  red,  or  blue  colour  reaction  with  concentrated 
sulphuric  acid.  The  behaviour  of  the  terpenes  with  regard  to  polarized 
light  is  very  interesting.  They  are  almost  all  optically  active,  and  most 
of  them  exist  both  in  dextro-  and  in  Isevo-rotatory  modifications.  While 
no  appreciable  alteration  (with  the  exception  of  the  resulting  optical 
inactivity)  is  apparent  upon  mixing  equivalent  amounts  of  dextro-  and 
Isevo-pinenes  or  of  dextro-  and  Itevo-camphenes,  there  results,  oddly 
enough,  when  dextro-  and  Isevo-limonene  are  mixed  together,  a  di- 
pentene  which  differs  materially  from  these  in  (higher)  boiling  point,  in 
melting  point,  and  in  the  lesser  solubility  of  its  derivatives  {e.g.  tetra- 
bromide,  see  table) ;  it  was  consequently  formerly  looked  upon  as  an 
individual  terpene,  viz. ,  dipentene. 

The  terpenes  are  widely  distributed  in  the  vegetable  king- 
dom, especially  in  the  coniferse  (Pinus,  Picea,  Abies,  etc.),  in 
the  varieties  of  Citrus,  etc.  The  products  which  are  isolated 
in  the  first  instance  from  the  individual  plants,  and  which 
according  to  their  source  are  designated  terpene,  citrene 
(from  oil  of  citron),  hesperidene  (from  oil  of  orange),  thymene 
(from  thyme),  carvene  (from  oil  of  cumin),  eucalyptene, 
olibene,  etc.,  have  for  the  most  part  the  formula  C^oHig  and 
approximately  equal  boiling  points  (160-190°) ;  they  are  not, 
however,  chemical  individuals  but  mixtures  of  isomeric  com- 
pounds. 

The  terpenes,  which  up  to  now  have  been  prepared  pure, 
differ  from  one  another  not  only  in  boiling  point  but  also  in 
the  fact  that  some  of  them  yield  liquid  and  others  solid 
bromine  addition  products  (in  the  latter  case  with  4  Br-atoms) 
of  definite  melting  point ;  further,  in  that  some  of  them  are 
only  capable  of  combining  with  one  but  others  with  two  mole- 
cules of  hydrochloric  acid  to  liquid  or  solid  hydrochlorides ; 
lastly,  in  that  only  some  of  them  yield  crystalline  compounds 
(nitrites)  with  NgOg  (0.  H^allach,  A.  227,  277  3  230,  225 ;  239, 
1 ;  246,  221,  etc.). 


506 


XXXV.  TERPENES  AND  CAMPHORS. 


Summary. 


M.  Pt. 

B.  Pt. 

Bromides, 
M.  Pt. 

Hydrochlorides, 
M.  Pt. 

Nitrites, 
M.  Pt. 

1. 

Pinene  . 

Liq. 

159-160° 

Liq. 

+  HOI  :  125° 

2. 

Camphene  . 

49° 

160-161° 

Liq. 

,,     :  decomp. 

— 

3. 

3\ 

Dipentene  . 
±Limonene 

Liq. 
>) 

180-182° 
175° 

Br4  : 125° 
„  104° 

I+2HC1  :50° 

— 

4. 

Sylvestrene 

>> 

1 /o-l /o 

„  135 

„      :  72 

5. 

Terpinolene 

»> 

185-190° 

„  116° 

[  „  :50T 

6. 

Terpinene  . 

»» 

180° 

155° 

7. 

Phellandrene 

»> 

about  170° 

94° 

As  is  seen  from  the  above  table,  dififerent  isomers  yield  the  same 
dipentene  hydrochloride  (M.  Pt.  50°)  on  combination  with  2HC1,  which 
would  indicate  that  they  contain  the  same  carbon  chain  (see  p.  511). 

In  addition  to  the  "Terpenes  proper,"  CioHjg,  we  have  Hemiterpenes, 
CgHg  (see  Isoprene),  which  polymerize  to  terpenes  (dipentene),  and  Poly- 
terpenes,  (CsHs)!,  e.^.  Cedrene,  Cubebene,  C15H24  (B.  Pt.  250-260°), 
Colophene,  C20H32  (B.  Pt.  above  300°),  and  Caoutchouc,  (CioHi6)x. 


1.  Pinene,  C^oH^g,  is  the  chief  constituent  of  German  and 
American  oil  of  turpentine,  oil  of  juniper,  of  eucalyptus,  of 
sage,  etc.  It  forms,  together  with  sylvestrene  and  dipentene, 
Russian  and  Swedish  turpentine  oil. 

Oil  of  turpentine  is  obtained  by  distilling  turpentine,  the 
resin  of  pines,  with  steam,  colophonium  (fiddle  resin)  remain- 
ing behind.  It  is  a  colourless  strongly  refracting  liquid  of 
characteristic  odour,  almost  insoluble  in  water  but  readily 
soluble  in  alcohol  and  ether.  It  dissolves  resins  and 
caoutchouc  (being  therefore  used  for  the  preparation  of  oil 

*  Identical  with  dipentene  dihydrochloride. 


PINENE;  CAMPHENE;  DIPENTENE. 


507 


paints,  lakes,  etc.),  also  sulphur,  phosphorus,  etc.  It  absorbs 
oxygen  from  the  air  with  the  formation  of  ozone  and  pro- 
duction of  resin,  minute  quantities  of  formic  acid,  cymene,  etc. 
being  formed  at  the  same  time.  Dilute  nitric  acid  either  gives 
rise  to  terephthalic  acid  in  addition  to  fatty  acids,  or — under 
other  conditions — to  terpenylic  acid,  G^H^fi^  (which  belongs 
to  the  fatty  series),  etc.  Heating  with  iodine  transforms  it 
into  cymene,  the  action  being  violent,  and  heating  with 
hydriodic  acid  into  the  compounds  C^oH^g  and  G-j^oH^o- 

Oil  of  turpentine  shows  physical  differences,  according  to  the  source 
from  which  it  is  derived,  the  German,  French  and  Venetian  oils  being 
Isevo-  and  the  Australian  dextro-rotatory.  These  differences  depend 
upon  the  existence  of  Isevo-  and  dextro-pinenes,  etc.  (cf.  the  tartaric 
acids).    B.  Pt.  158-161°;  Sp.  Gr.  0-86-0*89. 

Pinene  hydrochloride,  CioH^^yCl  (see  table,  p.  506)  is  a  solid 
white  crystalline  mass  with  a  camphor-like  odour,  whence  its 
name  of  artificial  camphor,"  insoluble  in  water  but  readily 
soluble  in  alcohol.  If  its  'hydrochloric  acid  is  separated  by 
weak  alkali,  e.g.  by  heating  it  with  soap,  camphene  is  obtained 
(see  below). 

Further  addition  of  HCl  does  not  lead  to  a  di-hydrochloride  of 
pinene  but  to  an  isomer,  dipentene-dihydrochloride.  From  this  it  may 
be  concluded  that  pinene  has  only  one  double  bond  in  the  molecule, 
and  the  same  applies  to  camphene. 

2.  Camphene,  C^oH^g,  of  which  there  are  two  modifications, 
dextro-  and  laevo-,  is  a  solid  terpene.  It  is  obtained  by 
heating  pinene  mono-hydrochloride  with  alcoholic  potash  or 
with  dry  soap,  and  is  more  stable  than  pinene. 

It  also  results  in  an  analogous  manner  from  Bornyl  chloride,  CioHj^Cl 
(see  Borneo  camphor).  It  has  an  odour  like  that  of  oil  of  turpentine 
and  camphor,  and  is  oxidized  to  camphor  by  chromic  acid  mixture. 
With  bromine  it  does  not  yield  a  tetrabromide  but  a  mono-substitution 
product,  and  it  combines  with  only  one  molecule  of  hydrochloric  acid. 

3.  Dipentene,  cine^ie,  inactive  Umonene,  is  found  (e.g.)  together 
with  cineol  in  Oleum  Cinae,  and  is  prepared  by  heating 
pinene,  camphene,  sylvestrene  or  limonene  to  250-270°  for 
several  hours,  and  also  by  the  abstraction  of  2 HCl  from  its 
di-hydrochloride  (which  is  formed  from  various  terpenes  by 


508 


XXXV.  TERPENES  AND  CAMPHORS. 


the  addition  of  2HC1).  It  is  further  produced  from  pinene 
under  the  influence  of  dilute  alcoholic  sulphuric  acid,  from 
terpin  hydrate  by  the  separation  of  water,  by  the  polymeriza- 
tion of  isoprene,  and,  together  with  the  latter  substance,  on 
distilling  caoutchouc.  It  has  a  pleasant  odour  like  that  of  oil 
of  citron,  and  is  more  stable  than  pinene  or  dextro-limonene, 
although  it  can  still  be  inverted  to  terpinene  by  alcoholic 
sulphuric  acid.  Its  tetra-bromide  results  from  the  combina- 
tion of  the  tetrabromides  of  dextro-  and  Isevo-limonene. 

Dipentene  di-hydrochloride,  CioH^gClg,  crystallizes  in 
rhombic  tables,  M.  Pt.  50°,  and  is  very  readily  soluble  in  hot 
alcohol.    Its  formation  has  already  been  given. 

Terpin  hydrate,  CjoHooOo  +  HgO,  =  CjoHiglOHja,  is  formed  when 
the  sohition  of  di-pentene  di-hydrochloride  in  aqueous  alcohol  is  allowed 
to  stand,  and  also  from  pinene  and  water  under  the  influence  of  certain 
acids.  It  crystallizes  in  large  rhombic  colourless  crystals,  M.  Pt.  117°, 
which  lose  their  water  at  lOO''.  The  compound  thus  formed,  Terpin, 
CioHi8(OH)2  (needles,  M.  Pt.  105°),  possesses  the  character  of  glycol 
and  yields  the  above  dichloride  again  with  hydrochloric  acid.  By  the 
separation  of  H2O  it  goes  into  Terpineol,  CioHi7(OH),  an  unsaturated 
monatomic  alcohol  which  is  transformed  by  bromine  into  dipentene 
tetrabromide.  Further  elimination  of  HgO  from  terpineol  (by  boiling 
it  with  dilute  acids)  gives  rise  to  dipentene,  terpinene,  or  terpinolene  as 
the  principal  product,  according  to  the  conditions  of  the  experiment. 

3a.  Limonene,  hesperidene^  citrene,  or  carvene.  The  oil  of  the  orange 
rind  consists  almost  entirely  of  dextro-limonene,  which  closely  resembles 
pinene,  but  differs  sharply  from  the  latter  in  its  tetrabromide  (see  table, 
p.  506).  Dextro-limonene  is  likewise  the  chief  constituent  of  carvene, 
oil  of  dill,  oil  of  erigeron,  etc.  ;  together  with  pinene  it  forms  oil  of 
citron.  Lsevo-limonene  is  present  together  with  Isevo-pinene  in  the  oil 
of  fir  cones.  The  +  and  -  tetrabromides  are  identical,  except  that 
their  crystals  are  the  mirror  images  of  one  another.  Dextro-limonene 
is  very  easily  rendered  inactive. 

4.  Silvestrene,  B.  Pt.  173-175°,  is  the  (dextro-rotatory)  chief  constituent 
of  Swedish  and  Russian  oil  of  turpentine.  Its  Di-hydrochloride  is 
isomeric  with  dipentene  di-hydrochloride  and  is  dextro-rotatory.  Sylves- 
trene  is  one  of  the  most  stable  of  the  terpenes.  It  gives  a  magnificent 
blue  colour  reaction  with  acetic  anhydride  and  concentrated  sulphuric 
acid. 

5.  Terpinolene,  which  is  very  like  dipentene,  and  : 

6.  Terpinene  both  result  from  the  '  *  isomeration "  of  pinene  (see 
terpin  hydrate).    Terpinene  and  also  : 


CAOUTCHOUC;  CAMrHOR. 


509 


7.  Phellandrene,  which  occurs  as  dextro-phellandrene  in  water 
dropwort  (Pliellandrium  aquaticum)  and  as  Isevo-phellandrene  in 
eucalyptus  oil,  yield — in  contradistinction  to  the  above  terpenes — 
compounds  with  nitrous  acid.  Phellandrene  is  among  the  most  easily 
altered  of  the  terpenes ;  it  is  radically  changed  by  contact  with  acids 
and  readily  converted  into  dipentene. 

8.  Caoutchouc,  (CiQHig)^,  is  the  hardened  milky  juice  of  the 
tropical  euphorbiaceae,  apocyneae,  etc.,  especially  Siphonia 
(ficus)  elastica,  which  grows  in  Brazil,  etc.  It  can  be  obtained 
pure,  in  the  form  of  a  white  amorphous  mass,  by  dissolving  the 
crude  material  in  chloroform  and  precipitating  with  alcohol. 
For  its  behaviour  on  distillation,  see  dipentene.  It  absorbs 
oxygen  from  the  air  and  is  converted  into  vulcanite  on  treat- 
ment with  sulphur. 

Guttapercha  (from  Isonandra  Gutta,  which  grows  in  India) 
is  related  to  camphor. 

Homologues  of  the  terpenes  have  also  been  prepared.  For 
their  constitution,  see  under  camphor. 

B.  Camphors. 

The  most  important  variety  of  camphor  is  : 

1.  Common  or  Japan  Camphor,  CioH^gO,  which  is  found 
in  the  camphor  tree  (Laurus  Camphora)  and  can  be  obtained 
from  the  latter  by  distillation  with  steam.  It  forms  colourless 
transparent  and  readily  sublimable  glancing  prisms  of  chara- 
teristic  odour;  M.  Pt.  175°,  B.  Pt.  204°,  Sp.  Gr.  0-985.  It  is 
dextro-rotatory  in  alcoholic  solution,  the  amount  of  rotation 
varying  with  the  source  of  the  camphor.  When  distilled  with 
phosphoric  anhydride  it  goes  into  cymene,  zinc  chloride  having 
the  same  effect,  though  in  the  latter  case  the  reaction  is  less 
simple  : 

Heated  with  iodine  it  yields  carvacrol,  i.e.  oxy-cymene  (p.  388),  just 
as  oil  of  turpentine  yields  cymene.  Nitric  acid  oxidizes  it  to  the 
dibasic  Camphoric  acid,  C8Hj4(C02H)2  (which  somewhat  resembles 
phthalic  acid),  and  then  to  Camphoronic  acid,  CyHi^Og,  etc.  Camphor 


510 


XXXV.  TERPENES  AND  CAMPHORS. 


reacts  with  hydroxylamine  to  produce  Camphor-oxime,  CioH^g(NOH), 
and  therefore  in  all  likelihood  contains  a  carbonyl  group.  The  oxime 
can  give  up  water  and  thus  go  into  the  Cyanide,  CgHjg.CN,  which 
yields  Campholenlc  acid,  CgHjg.COgH,  on  saponification,  and  Camphyl- 
amine,  CgHiglCHg.NHg),  on  reduction. 

For  the  constitution  of  camphor  see  B.  21,  1125. 
Camphor  may  be  prepared  artificially  by  oxidizing  camphene 
(p.  507). 

Two  Dichlorides,  CjoHigCla,  result  upon  treating  camphor  with 
phosphorus  pentachloride.  Chloro-,  Bromo-,  Nitro-  and  Amido- camphors 
are  also  known  ;  likewise  [e.g.]  Ethyl- camphor. 

Absynthol  is  an  isomer  of  camphor,  and  Caryophyllin,  CgoHg^Oa,  a 
polymer. 

2.  Borneol  or  Borneo  Camphor,  CioH^gO,  occurs  in  nature 
(in  Dryobalanops  Camphora),  and  is  produced  by  the  action 
of  nascent  hydrogen  upon  Japan  camphor : 

CJio^ieO  +  H2  =  CiqHiqO. 
It  is  very  like  the  latter,  but  has  at  the  same  time  an  odour 
of  pepper.    It  crystallizes  in  hexagonal  plates,  M.  Pt.  198°, 
B.  Pt.  212°.    Oxidation  converts  it  in  the  first  instance  into 
camphor. 

Borneol  possesses  the  character  of  a  secondary  alcohol,  yielding  com- 
pound ethers,  etc.,  and  giving  with  PCI5  Bornyl  chloride,  C10H17CI  (M. 
Pt.  148^),  isomeric  with  pinene  hydrochloride  ;  bornyl  chloride  goes  into 
camphene  when  warmed  with  alkalies.  Borneol  comports  itself  as  a 
saturated  compound,  but  at  the  same  time  it  forms  unstable  addition 
products  with  bromine  and  halogen  hydride. 

Cineol,  the  chief  constituent  of  01.  cinae,  and  which  is  frequently 
found  accompanying  the  terpenes,  is  isomeric  with  borneol ;  M.  Pt.  -  1°, 
B.  Pt.  176°.  It  likewise  yields  an  unstable  HCl-compound  and  readily 
goes  into  dipentene.  Its  chemical  behaviour  seems  to  point  to  its 
being  constituted  similarly  to  ethylene  oxide. 

Terpineol  (from  terpin  hydrate,  and  present  in  certain  ethereal  oils), 
is  also  isomeric  with  borneol  and  is  nearly  related  to  dipentene ;  it 
results,  together  with  cineol,  from  terpin  hydrate,  as  given  at  p.  508. 

3.  Mint-camphor,  menthol,  G-^^qH^qO,  is  the  principal  con- 
stituent of  oil  of  peppermint  (Mentha  piperita).  It  is  a 
monatomic  alcohol  and  forms  a  crystalline  mass;  M.  Pt. 
42°,  B.  Pt.  213°. 


RESINS. 


511 


Comtitution  of  the  terpenes  and  camphors.  The  close  relation  of  the 
terpenes  and  camphors  to  cymene,  and  their  convertibility  into  tere- 
phthalic  acid  show  that  they  are  derivatives  of  cymene  ;  they  therefore 
contain  a  hydrogenized  benzene  nucleus  in  which  the  groups  CH3  and 
C3H7  are  in  the  para-position  to  one  another. 

The  terpenes  appear  to  be  dihydro-cymenes.  The  isomerism  among 
them  may  depend  upon  the  point  at  which  a  double  (or  diagonal  ?)  bond 
is  dissolved,  so  that  one  and  the  same  pinene  di-hydrochloride  (dichloro- 
hexa-hydro-cymene)  may  result  from  various  isomerides  upon  the 
addition  of  2HC1.  (Cf.  A.  230,  225).  Pinene  and  camphene  contain 
perhaps  one  double  and  one  diagonal  bond,  terpineol  a  double  bond 
(no  diagonal  one),  dipentene,  sylvestrene  and  terpinolene  two  double 
bonds  in  the  benzene  nucleus,  and  terpinene  and  phellandrene  perhaps 
one  such  in  the  side  chain  (cf.  Wallach,  loc.  cit.  ;  Goldschmidt,  B.  18, 
1733;  Briihl,  B.  21,  145,  457). 

Borneo  camphor,  CiqHisO,  seems  from  its  alcoholic  character  to  be 
an  oxy-tetrahydro-cymene  (containing  the  group  =  CH.OH)  ;  and 
Japan  camphor,  CioHigO,  to  be  the  corresponding  ketone  with  two 
atoms  of  hydrogen  less,  i.e.  a  keto-tetrahydro-cymene,  its  behaviour 
with  hydroxylamine  being  in  accordance  with  this  view.  Lastly, 
menthol  is  possibly  an  oxy-hexahydro-cymene. 

XXXVI.  RESINS;  GLUCOSIDES;  VEGETABLE 
SUBSTANCES 

(of  unknown  constitution). 
A.  Resins. 

Many  organic  compounds,  the  terpenes  in  particular,  possess 
the  property  of  becoming  "  resinified  "  by  oxidation  in  the  air 
or  under  the  influence  of  chemical  reagents,  i.e.  of  being 
converted  into  substances  very  similar  to  the  resins  which 
occur  in  nature.  These  natural  resins  are  solid,  amorphous, 
and  generally  vitreous  brittle  masses  of  conchoidal  fracture, 
insoluble  in  water  and  acids,  but  soluble  in  alcohol,  ether  and 
oil  of  turpentine.  They  are  found  naturally  in  abundance, 
partly  also  as  balsams,  i.e.  dissolved  in  terpenes  or  ethereal 
oils,  from  which  they  can  be  separated  by  distilling  with 
steam.  The  resins  dissolve  in  alkalies  to  form  compounds 
of  the  nature  of  soap  (resin  soaps),  being  again  precipitated 


512  XXXVI.  RESINS;  GLUCOSIDES;  VEGETABLE  SUBSTANCES. 

from  the  aqueous  solutions  of  these  on  the  addition  of  acids ; 
most  resins  must  therefore  consist  of  a  mixture  of  somewhat 
complicated  acids  (the  so-called  resin-acids). 

Abietic  acid  (C^qH^qO^  ?)  is  an  individual  acid  which  has 
been  isolated  from  colophonium  (the  residue  from  the  distilla- 
tion of  turpentine,  see  below) ;  it  crystallizes  in  small  plates, 
M.  Pt.  165°,  and  is  soluble  in  hot  alcohol.  Pimaric  acid, 
C20H3QO2,  has  been  prepared  {e.g,)  from  galipot  resin  (Pinus 
maritima)  in  a  similar  way;  M.  Pt.  148°.  It  closely  resembles 
abietic  acid,  is  crystalline  and  forms  crystalline  derivatives, 
and  exists  in  two  modifications,  dextro-  and  laevo-pimaric 
acids. 

The  resins  show  their  relation  to  the  aromatic  compounds  by  being 
converted  into  hydrocarbons  of  the  benzene  or  naphthalene  series  when 
distilled  with  zinc  dust,  and  by  the  formation  (e.g.)oi  dioxy-  and  trioxy- 
benzenes  when  they  are  fused  with  potash. 

In  addition  to  Colophonium,  there  may  be  mentioned 
among  other  resins  Shellac  (from  East  Indian  Ficus  varieties), 
and  Amber,  a  fossil  resin  which  contains  succinic  acid  in 
addition  to  resin-acids  and  a  volatile  oil. 

The  resins  are  largely  used  for  the  manufacture  of  lacs, 
varnishes,  etc. 

B.  Glucosides. 

(Cf.  0.  Jacohsen^s  "Die  Glucoside,"  Breslau,  Trewendt.) 

As  glucosides  are  designated  a  series  of  vegetable  substances 
which  are  so  broken  up  by  alkalies,  acids,  or  ferments,  that 
one  of  the  products  of  this  decomposition  is  a  glucose,  usually 
grape  sugar.  They  are  thus  ethereal  derivatives  of  the  sugar 
varieties  in  question.  Some  of  them  have  been  mentioned 
already. 

Amygdalin,  C20H27NO11  (p.  398),  is  found  in  bitter  almonds, 
in  the  leaves  of  the  cherry  laurel,  in  the  kernels  of  the  peach, 
cherry  and  other  amygdalaceae.  It  crystallizes  in  colourless 
prisms,  M.  Pt.  200°,  is  readily  soluble  in  water,  and  breaks  up 


GLUCOSIDES. 


513 


into  oil  of  bitter  almonds,  dextrose  and  hydrocyanic  acid  under 
the  influence  of  emulsin  (p.  294),  or  when  saponified. 

Among  others  there  may  be  mentioned  : 

Salicin,  CigHigOy,  found  in  varieties  of  SaHx,  which  breaks  up  into 
saligenin  (o-oxy-benzyl  alcohol)  and  dextrose  ;  Helicin,  Ci^K^qO^  +  HgO, 
which  results  from  the  action  of  N2O3  upon  salicin  and  is  decomposable 
into  salicylic  aldehyde  and  glucose,  from  which  it  can  again  be  obtained 
synthetically ;  Populin  or  benzoyl- saligenin,  CioH2203  (in  varieties  of 
Populus),  which  can  be  prepared  artificially  from  benzoyl  chloride  and 
salicin. 

Arbutin,  Ci2Hig07,  and  Methyl-arbutin,  CigHigOy,  present  in  the 
leaves  of  the  bear  berry,  etc. ,  break  up  into  dextrose  and  hydroquinone 
or  methyl-hydroquinone  respectively. 

Hesperidin,  C22H26O125  which  is  contained  in  unripe  oranges,  etc., 
can  be  decomposed  into  dextrose,  iso-ferulic  acid  (isomeric  with  ferulic 
acid,  p.  427),  and  phloroglucin. 

Phloridzin,  C21H24O10  (fine  prisms),  found  in  the  bark  of  fruit  trees, 
can  be  split  up  into  grape  sugar  and  Phloretin,  CigH^405,  and  this  latter 
— in  its  turn — into  phloretic  acid  and  phloroglucin  (p.  391). 

Aesculin,  CigHigOQ  (prisms),  present  in  the  bark  of  the  horse  chestnut, 
is  decomposed  by  acids  into  grape  sugar  and  Aesculetin  (dioxy-cumarin, 
p.  428), 

Saponin,  C32Hg40i8  (in  the  soapwort). 

Quercitrin,  C36H38O20,  found  in  Quercus  tinctoria,  chestnut  blossoms, 
etc.  ;  yellow  needles. 

Coniferin,  C16H22O8  +  2H2O  (in  the  cambium  sap  of  the  coniferae), 
breaks  up  into  glucose  and  coniferyl  alcohol,  and  serves  for  the  pre- 
paration of  vanillin,  which  results  from  it  upon  oxidation  (p.  401). 

Myronic  acid,  C10H19O10NS2,  is  present  as  potassium  salt, 
C10H18KO10NS2  (glancing  needles),  in  black  mustard  seed.  It  is 
broken  up  into  grape  sugar,  potassium  bisulphate  and  allyl  iso- 
thiocyanate  by  baryta  water  or  by  the  ferment  Myrosin,  which 
likewise  occurs  in  the  mustard  seed. 

Ruberythric  acid  ;  see  p.  474. 

For  synthetized  glucosides,  see  B.  18,  1960,  3481. 


O.  Vegetable  substances  of  unknown  Constitution. 


Aloin,  C17H18O7  (in  the  aloe  plant),  crystallizes  in  fine  needles  and  is 
a  powerful  purgative  ;  it  is  a  derivative  of  anthracene. 

(506)  2K 


514  XXXVII.  ALBUMINOUS  SUBSTANCES;  ANIMAL  CHEMISTRY. 


Cantharidin,  C10H12O4  (in  Spanish  fly),  forms  sublimable  plates ; 
it  blisters  the  skin. 

Picrotoxin,  C30H34O13  (in  the  seeds  of  Cocculus  indicus). 

Santonin,  C15H18O3  (in  worm  seed),  is  derived  from  naphthalene  (B. 
16,  2686). 

Among  natural  dyes  of  unknown  constitution  we  have  : 

Brasilin,  C16H14O5,  the  red  dye  of  Brazil  and  Fernambuco  woods.  In 
the  free  state  it  crystallizes  in  colourless  glancing  needles. 

Curcumin,  C14H14O4  ?,  the  yellow  dye  of  the  turmeric  root,  is  turned 
brownish-red  by  alkalies,  for  which  it  forms  a  delicate  test. 

Hsematoxylin,  C16H14O6,  is  the  colouring  matter  of  logwood  (Hsema- 
toxylon  Campechianum).  It  forms  yellowish  prisms,  which  dissolve  in 
alkalies  with  a  violet-blue  colour. 

Carminic  acid,  C17H18O10,  the  active  principle  of  cochineal  (Coccus 
Cacti),  is  a  red  amorphous  mass  which  is  split  up  by  acids  into  a  sugar 
(not  glucose)  and  Carmine  red,  C11H12O7,  the  latter  forming  a  purple-red 
mass  with  a  green  reflection;  bromine  converts  carminic  acid  into  a 
dibromo- derivative  of  a  methylated  and  hydroxylated  phthalic  acid 
(B.  18,  3180). 

Harmin,  C13H12N2O,  and  Harmalin,  C13H14N2O,  are  the  colouring 
matters  of  Peganum  Harmala  (B.  18,  400). 

Chlorophyll  or  Imf  green,  is  the  green  colouring  matter  of  plants,  and 
contains  iron  in  its  molecule.  Together  with  starch,  wax,  etc.,  it 
forms  the  chlorophyll  granules  of  the  cells,  but,  notwithstanding  that 
it  has  been  the  subject  of  numerous  investigations,  its  nature  is  not  yet 
accurately  known. 

Litmus  is  a  blue  dye  obtained  from  Roccella  tinctoria  and  other 
lichens ;  it  is  related  to  orcein  (p.  390),  and  is  turned  red  by  acids,  the 
blue  colour  being  restored  by  alkalies.  Hence  it  is  much  used  as  an 
indicator  in  alkalimetry. 


XXXVII.  ALBUMINOUS  SUBSTANCES; 
ANIMAL  CHEMISTRY. 

An  extended  description  of  the  substances  (other  than  those 
abeady  mentioned)  which  are  found  in  the  animal  organism  and 
which  are  therefore  of  importance  for  physiological  chemistry, 
will  not  be  attempted  here,  since  they  are  for  the  most  part 
better  known  from  a  physiological  than  from  a  chemical  point 


THE  ALBUMENS. 


515 


of  view.  Only  the  albumens  and  albuminoids,  both  of  which 
are  classed  as  proteids,  and  some  of  the  substances  which  are 
produced  during  metabolic  processes,  will  be  treated  of. 

A.  Albumens. 

The  albumens  make  up  the  chief  part  of  the  organism,  being 
present  partly  in  the  soluble  and  partly  in  the  solid  state; 
they  are  found  in  all  the  nutritive  fluids  of  the  body.  In 
solution  they  are  opalescent,  optically  ( - )  active,  and  do  not 
diffuse  through  parchment  paper,  i,e,  are  colloids;  but  they 
are  thrown  down  when  the  solution  is  warmed,  or  upon  the 
addition  of  strong  mineral  acids,  of  many  metallic  salts  [e.g, 
copper  sulphate,  basic  lead  acetate  and  mercuric  chloride],  of 
alcohol,  tannic  acid,  acetic  acid  together  with  a  little  potassium 
ferrocyanide,  etc.  When  boiled  :  (a)  with  nitric  acid,  they  are 
coloured  yellow  (the  xantho-protei'n  reaction) ;  (b)  with  a  solu- 
tion of  mercuric  nitrate  containing  N2O3  (Millon^s  reagent),  red; 
(c)  with  caustic  soda  solution  and  a  very  little  cupric  sulphate, 
violet.  The  albumens  combine  both  with  acids  and  alkalies  to 
acid-  and  alkali-albuminates  (see  below). 

The  different  albumens  vary  only  slightly  among  themselves 
in  percentage  composition ;  they  contain  : 

C  =  52.7  to  54.5  p.c;  H  =  6.9  to  7.3  p.c;  N  =  15.4:  to  16.5  p.c; 
0  =  20.9  to  23.5  p.c;  and  S  =  0.8  to  2.0  p.c. 

Since  they  have  not  yet  been  obtained  pure,  it  is  impossible 
to  give  a  formula  for  them,  even  for  the  crystalline  albumen 
which  occurs  in  hemp,  castor  oil,  and  pumpkin  seeds  (see  B. 
15,  953). 

The  fact  that  albumen  contains  sulphur  is  worthy  of  note, 
though  the  mode  in  which  it  is  combined  in  the  molecule  is 
unknown ;  warming  with  a  dilute  alkaline  solution  is  sufficient 
to  eliminate  it  partially,  e.g.  when  white  of  egg  is  boiled  with 
an  alkaline  solution  of  lead  oxide,  sulphide  of  lead  is  separated 
(the  test  for  sulphur  in  albumen). 

Constitution.    The  way  in  which  albumen  is  split  up  by  acids 


516  XXXVII.  ALBUMINOUS  SUBSTANCES;  ANIMAL  CHEMISTRY. 


(especially  in  presence  of  stannous  chloride),  or  by  baryta 
water,  gives  some  indication  of  its  constitution.  Here,  in 
addition  to  ammonia  and  carbonic  acid,  amido-acids  are  the 
principal  products,  and  these  belong  not  only  to  the  fatty 
series  [e.g,  glycocoll,  leucine,  aspartic  acid,  glutamic  acid  and 
^qeucein,"  (C4H7N02)^  (B.  19,  Eef.  30)],  but  also  to  the 
aromatic  {e.g,  phenyl-amido-propionic  acid  and  tyrosine). 

Loew's  hypothesis  that  albumen  is  essentially  a  condensation  product 
of  aspartic  aldehyde,  C4H7NO2,  ^.  c.  of  leucein,  is  worthy  of  mention. 

The  putrefaction  of  albumen  gives  rise  not  only  to  amido- 
acids  but  also  to  other  aromatic  and  fatty  acids  {e.g.  butyric 
acid),  indole,  skatole  and  cresol ;  further,  to  the  alkaloid-like 
Ptomaines  (the  poisonous  alkaloids  produced  in  dead  bodies), 
of  which  neurine  and  pentamethylene-diamine  (or  **Cadaverin," 
B.  19,  2585)  have  been  isolated. 

Albuminous  matters  undergo  change  when  acted  upon  by  the  juices 
of  the  stomach  at  a  temperature  of  30-40°,  pepsin  converting  them  in 
the  first  instance  into  Anti-  and  Hemi-albumoses,  both  of  which  then 
go  into  peptone ;  trypsin  likewise  gives  rise  to  the  two  above  album- 
oses,  but  then  transforms  the  anti-compound  into  peptone  and  the  hemi- 
compound  into  leucine,  tyrosine  and  asparagine  (the  pancreatic  diges- 
tion ;  for  details,  see  Kuh7ie,  B.  17,  Ref.  79).  The  peptones  are  readily 
soluble  in  water,  and  they  are  neither  coagulated  upon  heating  nor  by 
most  of  the  reagents  which  coagulate  albumen. 


Classification  of  the  albumens, 

1.  Those  which  are  soluble  in  water,  but  become  insoluble,  i.e, 
coagulate,  when  the  solution  is  heated  to  70-75°;  to  this  class  belong 
the  Albumens,  e.g,  egg  albumen,  serum  albumen,  vegetable  albumen, 
etc. 

2.  Those  insoluble  in  water  and  which  curdle  at  once  when  outside 
the  organism;  this  class  includes  the  Fibrins,  e.g,  blood  fibrin,  vege- 
table fibrin,  etc. 

3.  Those  insoluble  in  water  and  in  a  solution  of  sodium  chloride,  but 
readily  soluble  in  dilute  hydrochloric  acid  and  in  alkaline  carbonate ; 
they  are  neither  precipitated  on  boiling,  nor  on  neutralizing  the  dilute 
solution  in  presence  of  potassium  phosphate.  These  are  the  Albumin- 
ates, which  include  the  caseins,  e.g.  milk  casein  and  vegetable  casein 


THE  ALBUMINOIDS. 


517 


(legumin),  and  also  alkali-albuminate,  which  results  on  dissolving 
albumen  in  alkali. 

4.  Those  insoluble  in  water  but  soluble  in  a  dilute  solution  of  com- 
mon salt  or  sulphate  of  magnesia,  and  which  coagulate  on  heating  their 
solution  or  which  are  precipitated  on  saturating  it  with  MgS04  at  30°. 
These  are  the  Globulins,  e.g.  fibrinogene  and  fibrinoplastic  substance 
(which  combine  with  one  another  to  fibrin),  globulin  (in  the  crystalline 
lens  of  the  eye),  myosin  (muscle  albumen)  and  vitellin. 

5.  Those  which  are  insoluble  in  water  and  sodium  chloride  solution, 
but  readily  soluble  in  dilute  acids  and  alkalies  or  alkaline  carbonates, 
and  which  are  precipitated  on  neutralizing  the  solution  but  not  by  heat : 
Syntonin  (acid-albumen). 

6.  Hemi-albumoses  and  Peptones  (see  above). 


B.  Albuminoids. 

The  albuminoids  are  to  be  regarded  as  the  nearest  deriva- 
tives of  the  albumens,  being  closely  related  to  these ;  they  are 
mostly  organized,  and  are  important  constituents  of  the  tissue. 
Some  of  them  are  converted  into  glue  when  boiled  with  water, 
and  hence  are  termed  glue-yielding  substances.    They  give 

bone  oil "  (p.  480)  on  destructive  distillation. 

To  this  group  belong : 

1.  Glutin  or  Bone  glue,  known  as  gelatine  in  the  pure 
state,  which  is  characterized  by  its  solution  solidifying  to  a 
jelly  on  cooling ;  it  is  obtained  by  boiling  bone  cartilage, 
connective  tissue,  stages  horn,  calves'  feet,  etc.  (the  so-called 
"  collogenes  ")  with  water. 

2.  Chondrin  or  CartUage  glue,  which  closely  resembles  the  above, 
results  from  cartilage  proper  (which  is  termed  a  "  chondrogene  "). 

Neither  of  these,  unlike  the  albumens,  are  precipitated  from  the 
aqueous  solution  by  nitric  acid  or  potassium  ferrocyanide.  Tannic 
acid  throws  down  gelatine  from  solution,  and  unites  with  the  glue- 
yielding  substances  of  the  organism  to  form  compounds  insoluble  in 
water  (the  tanning  of  hide  ;  leather). 

Chondrin  is  precipitated  from  its  solution  by  many  salts  which  do 
not  throw  down  glutin,  e.g.  by  alum.  Bone  glue  yields  glycocoU  and 
leucine  when  boiled  with  acids,  and  chondrin  yields  leucine. 

Gelatine  is  for  the  most  part  transformed  into  the  ether  of  an 


518  XXXVII.  ALBUMINOUS  SUBSTANCES;  ANIMAL  CHEMISTRY. 

amido-acid  by  an  alcoholic  solution  of  hydrochloric  acid,  possibly  the 
compound : 

CH(NH2)=C(OH)-C02.C2H5,  Amido-oxy-acrylic  ether, 
so  that  it  is  permissible  to  surmise  that  gelatine  is  a  condensation 
product  of  amido-acrolein,  CH(NH2)=Cfl— CHO,  possessing  as  it  does 
the  same  percentage  composition  as  the  latter  (Curtius  and  Buchner, 
10,  850 ;  cf.  also  B.  19,  Ref.  697). 

3.  Mucin  or  Mucus,  found  in  slime  secretions,  is  free  from  sulphur. 

4.  Keratin  or  horn  substance  goes  to  build  up  the  epidermis,  nails, 
hair,  etc.  ;  it  contains  sulphur. 

5.  Elastin  is  the  chief  constituent  of  the  elastic  ligaments  of  the 
organism.  It  does  not  contain  sulphur,  and  yields  leucine  with 
sulphuric  acid. 

6.  The  unorganized  ferments  diastase,  ptyalin,  pepsin,  trypsin,  etc., 
already  mentioned  at  p.  294,  also  belong  to  this  group. 

7.  Chitin,  the  principal  constituent  of  the  cuticular  covering 
of  the  articulata,  e.g.  of  the  shell  of  the  crab,  differs  from  horn 
substance  in  being  insoluble  in  alkalies ;  it  yields  glucosamine 
(p.  289)  when  boiled  with  acids. 

0.  Compounds  of  a  higher  order  than  Albumen. 

1.  Colouring  matters.  Haemoglobin,  the  chief  constituent 
of  the  red  blood  corpuscles,  probably  possesses  a  still  more 
complicated  composition  than  albumen,  since  it  gives  albumen 
and  heematin  (the  colouring  matter  of  blood)  when  broken 
up.  Haemoglobin  combines  very  readily  with  oxygen,  e.g. 
in  the  lungs,  to  Oxy-haemoglobin,  which  yields  up  its  oxygen 
again,  not  only  in  the  organism  but  also  in  a  vacuum  and 
when  exposed  to  the  action  of  re  ducing  agents.  With  carbon 
monoxide  it  combines  to  the  compound,  Carbon  monoxide- 
haemoglobin.  All  three  compounds  can  be  obtained  crystal- 
lized in  the  cold,  and  they  possess  characteristic  absorption- 
spectra.  Hsematin  (G^^^^^eO^V}^  a  dark  brown  powder 
containing  8  p.c.  of  iron,  results  even  from  the  spontaneous 
decomposition  of  haemoglobin.  Its  hydrochloride,  HsBmin 
(C32H3oN4Fe03,  HCl  ?),  is  obtained  in  the  form  of  characteristic 
microscopic,  reddish-brown  crystals  by  the  action  of  glacial 


NUCLEIN;  LECITHIN. 


519 


acetic  acid  and  some  common  salt  upon  oxy-hsemoglobin ;  this 
is  a  delicate  test  for  the  presence  of  blood. 

2.  Nuclein  is  an  important  constituent  of  the  cell  nucleus, 
e,g.  of  pus  cells,  of  nucleated  blood  corpuscles,  of  yeast  cells, 
etc.  It  forms  a  white  mass  insoluble  in  water  or  dilute  mineral 
acids  but  readily  soluble  in  alkalies.  It  contains  phosphoric 
acid  in  ethereal  combination,  and  breaks  up  when  boiled  with 
water  or  dilute  acids  into  albumen,  hypoxanthine  and  the  acid 
just  named.  Some  varieties  of  nuclein  are  free  from  sulphur 
while  others  contain  it,  the  latter  yielding  tyrosine  when  decom- 
posed. Nuclein  appears  to  be  formed  synthetically  when 
albumen  is  coagulated  by  meta-phosphoric  acid. 

D.  Substances  produced  during  Metabolic 
processes. 

1.  Acids  of  the,  bile.  Bile  contains  the  sodium  salts  of  Glyco- 
cholic  acid,  C26H43NO6,  and  Taurocholic  acid,  C26H45NSO7,  both  of 
which  are  decomposed  by  alkalies  into  Cholic  acid,  C24H40O5, 
=  C2iH32(OH)(C02H)(CH2.0H)2,  on  the  one  hand,  and  giycocoll  and 
taurine  respectively  on  the  other. 

2.  The  bile  also  contains  various  colouring  matters :  Bilirubin, 
Biliverdin,  Bilifuscin,  etc.  These  apparently  bear  some  simple 
relation  to  the  colouring  matter  of  blood,  the  formula  of  bilirubin 
being  C32H36N4O6  (see  B.  17,  2265). 

3.  The  Cholesterins,  C26H43(OH),  of  which  numerous  varieties  are 
now  known,  are  present  in  blood,  bile,  nerve  substance,  vegetable  fats, 
etc.    They  are  monatomic  alcohols. 

4»  Cerebrin,  C17H33NO3,  is  an  important  ingredient  of  the  medullary 
substance  of  the  nerve. 

Lecithin,  C42H84NO9P,  is  a  characteristic  constituent  of  nerve  sub- 
stance, brain,  yolk  of  egg,  etc.  It  forms  a  waxy  mass  capable  of 
crystallization,  which  dissolves  in  alcohol  and  ether,  and  swells  up 
to  an  opalescent  liquid  with  water.  It  breaks  up  on  saponification 
into  choline,  glycerine-phosphoric  acid,  stearic  and  palmitic  acids, 
and  is  therefore  to  be  regarded  as  glycerine  in  which  the  three 
hydroxyl  hydrogens  have  been  replaced  by  the  palmitic,  stearic  and 
phosphoric  acid  residues,  the  last  of  which  still  remains  in  ethereal 
combination  with  choline. 


INDEX. 


A 

a = asymmetric,  313. 
Abietic  acid,  512. 
Absynthol,  510. 
Acenaphthene,  468. 
Acetals,  132,  136. 
Acetaldehyde,  135. 
Acetamide,  183. 
Acetamido-chloride,  183. 
Acetamidine,  185. 
Acetanilide,  341,  357. 
Acetenyl-benzene,  332. 
Acetic  acid,  8,  156. 
Acetic  anhydride,  179. 
Acetic  ether,  175. 
Acetic  fermentation,  156. 
Acetimido-chloride,  183. 
Acetimido-hydrate,  185. 
Acetimido-thio-ethyl,  185. 
Acetimido-thio-hydrate,  184. 
Acetins,  202. 
Aceto-acetic  acid,  224. 
Aceto-acetic  aldehyde,  222,  321. 
Aceto-acetic  anilide,  493. 
Aceto-acetic  ether,  224. 
Aceto-acetic  ether  synthesis,  160, 
407. 

Aceto-malonic  ether,  227. 
Aceto-nitrile,  108. 
Aceto-phenone,  332,  399. 
Aceto-phenone-acetone,  400. 
Aceto-propionic  acid,  223. 
Aceto-succinic  ether,  227. 
Aceto-thiamide,  184. 
Acetol,  221. 
Acetone,  143. 
Acetone  alcohol,  221. 
Acetone-amines,  141. 
Acetone  cyanhydrin,  193. 
Acetone-dicarboxylic  acid,  224,  390. 
Acetone  phenyl'hydrazine,  436. 
Acetonic  acid,  217. 
Acetonyl-acetone,  221,  299. 
Acetoxime,  142,  144. 
Acet-toluide,  358. 
Aceturic  acid,  213» 


Acetyl,  153. 
Acetyl-acetone,  221. 
Acetyl-amido-benzoic  acid,  494. 
Acetyl  bromide,  178. 
Acetyl-carbinol,  221. 
Acetyl  chloride,  177. 
Acetyl-diphenylamme,  347. 
Acetyl-indole,  436. 
Acetyl-naphthols,  466. 
Acetyl  peroxide,  179. 
Acetyl -phenol,  382,  383. 
Acetyl-sulphanilic  acid,  353. 
Acetyl-thio-urea,  277. 
Acetyl-toluidines,  358. 
Acetyl-urea,  273. 
Acetylene,  56,  320. 
Acetylene-dicarboxylic  acid,  238. 
Acetylene  series,  53. 
Acid-albuminates,  515,  517. 
"  Acid  decomposition,"  225. 
Acid  derivatives,  173. 
Acid  fuchsine,  453. 
Acid  green,  453. 
Acid  violet,  453. 
Acids,  aromatic,  401  et  seq.,  428. 
Acids,  fatty,  146  et  seq. 
Aconitic  acid,  246. 
Acridine,  355,  478,  498. 
Acridine-carboxylic  acid,  499. 
Acridinic  acid,  497. 
Acridyl  aldehyde,  499. 
Acrolein,  137. 
Acrolein-ammonia,  138. 
Acrolein-aniline,  492. 
Acroses,  289. 
Acrylic  acid,  164,  165. 
Adenine,  284. 
Adipic  acid,  228.  * 
iEsculin,  513. 
iEsculetin,  428. 
Affinities,  free,  16,  49. 
Alanine,  216. 
Albuminates,  516. 
Albumens,  515. 
Albumenoids,  517. 
Alcohol,  79. 

Alcohol,  constitution  of,  17. 


522 


INDEX. 


Alcohol-acids,  206,  402,  403. 
Alcohol  of  crystallization,  78. 
Alcohols,  aromatic,  395. 
Alcohols,  fatty,  70. 
Aldehyde,  135. 

Aldehyde-acids,  205,  212,  222. 

Aldehyde-alcohols,  220,  286. 

Aldehyde  "condensations,"  133. 

Aldehydes,  aromatic,  398. 

Aldehydes,  fatty,  128. 

Aldehydes,  the  fuchsine  test  for,  135,  452. 

Aldehydine,  350,  482,  487. 

Aldine,  491. 

Aldines,  143. 

Aldol,  134,  220,  492. 

Aldol  "  condensations,"  134,  408. 

Aldoximes,  134,  406. 

Alizarin,  472,  474. 

Alizarin  black,  467. 

Alizarin  blue,  475. 

Alizarin  orange,  475. 

Alkali-albuminate,  517. 

Alkali  blue,  453. 

Alkaloids,  481,  499. 

Alkaloids  from  dead  bodies,  516. 

Alkarsin,  124. 

Alkeins,  196. 

Alkines,  196. 

Alkyl,  37. 

Alkyl-hydro-anthracenes,  472. 
Alkyl-hydro-anthranols,  472. 
Alkyl-malonic  acids,  230. 
Alkylenes,  46. 
AUantoin,  280,  283. 
Allan turic  acid,  280. 
AUene,  55,  57. 
AUophanic  acid,  273. 
Alloxan,  280,  282. 
Alloxanic  acid,  280,  282. 
Alloxantin,  280,  282. 
Allyl-acetic  acid,  166. 
AUyl  alcohol,  87. 
AUyl-aniline,  494. 
Allyl  bromide,  60,  70. 
Allyl  chloride,  60,  70. 
Allyl  cyanide,  108. 
Allyl  ether,  92. 
Allyl  iodide,  60,  70. 
Allyl  "  mustard  oil,"  262. 
AUyl-pyridine,  ^7. 
Allyl  sulphide,  97. 
Allyl  thiocyanate,  262. 
Allylene,  55,  57,  320. 
Aloin,  513. 

Alpha-compounds  (see  individually). 
Aluminium  chloride,  action  of,  324. 
Aluminium  methide,  128. 
Amalic  acid,  283. 
Aniber,  512. 

"Amidating,"  842.  ' 


Amides  of  the  fatty  series,  180. 

Amidines,  185. 

Amido-acetic  acid,  212. 

Amido-acetone,  143. 

Amido-acids,  208,  212. 

Amido-acrdlein,  518. 

Amido-azo-benzene,  368,  370. 

Amido-azo-benzene-sulphonic  acid,  371. 

Amido-azo-compounds,  363,  365,  368. 

Amido-azo-naphthalene,  465. 

Amido-azo-phenylene,  350. 

Amido-azo-toluenes,  371. 

Amido-benzaldehyde,  399,  493. 

Amido-benzene,  340,  350. 

Amido-benzene-sulphonic  acids,  375. 

Amido-benzoic  acids,  308,  358,  402,  414. 

Amido-benzoyl-formic  acid,  424. 

Amido-butyric  acids,  217. 

Amido-camphor,  510. 

Amido-caproic  acid,  217. 

Amido-chlorides,  183. 
Amido-cinnamic  acids,  418,  492. 
Amido-cinnamic  aldehyde,  492. 
Amido -derivatives,  aromatic,  340. 
Amido-dimethyl-aniline,  341,  354,  356. 
Amido-diphenyl,  438. 
Amido-diphenylamine,  341,  355. 
Amido-durene,  359. 
Amido-ethyl-benzenes,  359. 
Amido-ethyl-sulphonic  acid,  197. 
Amido-hydrocinnamic  acid,  417. 
Amido-isobutyl-benzene,  343,  359. 
Amido-ketones,  143. 
Amido-mesitylene,  359. 
Amido-naphthols,  446. 
Amido-oxy-acrylic  ether,  518. 
Amido-phenols,  382,  386. 
Amido-phenyl-acetic  acids,  416. 
Amido-phenyl-methyl-quinoline,  497. 
Amido-phthalic  acid,  429. 
Amido -propionic  acid,  216. 
Amido-propyl-benzene,  359. 
Amido-pseudo-cumene,  359. 
Amido-quinolines,  480,  496. 
Amido-succinic  acid,  239,  240. 
Amido-tetramethyl-benzenes,  359. 
Amido-thiazol,  302. 
Amido-thiophene,  297,  301. 
Amido-thio-phenols,  386. 
Amido-trimethyl-benzenes,  359. 
Amido-valeric  acids,  217. 
Amido-xylenes,  359. 
Amimides,  185. 
Amines,  aromatic,  340. 
Amines,  fatty,  110. 
Aminic  acids,  212. 
Amm elide,  265. 
Ammeline,  265. 
Ammonium  bases,  110, 115, 
Ammonium  cyanide,  254. 


INDEX. 


523 


Amygdalin,  252,  398,  612. 

Amyl  alcohols,  85. 

Arayl-bcnzenc,  323. 

Amyl  bromide,  66. 

Amyl  chloride,  60,  66. 

Amyl  iodide,  66. 

Amyl  nitrite,  100. 

Amylenes,  46. 

Amyloid,  293. 

Amylum,  293. 

Analysis,  qualitative,  2. 

Analysis,  quantitative,  4. 

Analysis,  elementary,  4. 

Angelic  acid,  164,  166. 

Anhydrides  of  the  fatty  acids,  178. 

Anhydro-bases,  349,  386. 

Anilides,  345,  357. 

Aniline,  341,  350. 

Aniline  black,  351,  503. 

Aniline  blue,  453. 

Aniline  red  (see  Fuchsine). 

Aniline  violet  (see  Methyl  violet). 

Aniline  yellow,  869. 

Animal  chemistry,  514. 

Anisic  acid,  410,  421. 

Anisic  alcohol,  400,  401. 

Anisic  aldehyde,  400,  401. 

Anisidine,  382,  386. 

Anisidine-sulphonic  acid,  382. 

Anisol,  382. 

Anthracene,  469. 

Anthracene-carboxylic  acids,  473. 

Anthracene  hydrides,  471. 

Anthracene-sulphonic  acids,  472. 

Anthrachrysone,  472. 

Anthraflavic  acid,  472,  474. 

Anthra-hydroquinone,  472,  473. 

Anthramine,  472,  473. 

Anthranil,  414. 

Anthranilic  acid,  414. 

Anthranol,  472,  473. 

Anthra-purpurin,  472,  475. 

Anthra-quinoline,  497. 

Anthraquinone,  470,  472,  473. 

Anthraquinone-sulphonic  acids,  472,  474. 

Anthrarufin,  472. 

Anthrol,  472,  473. 

Anti-albumoses,  516. 

Antimony  ethide,  126. 

Antimony  methide,  126. 

Antipyrine,  302. 

Apo-quinine,  500. 

Aposorbic  acid,  243. 

Arabic  acid,  294. 

Arabin,  294. 

Arabinose,  220. 

Arachinic  acid,  147. 

Arbutin,  513. 

Aromatic  compounds,  V.  Meyer's  defini- 
tion of,  806. 


Aromatic  compounds,  303. 
Aromatic  hydrocarbons,  323. 
Aromatic  hydrocarbons,  isomers  and  con- 
stitution, 325. 
Arsenic  compounds,  122. 
Arsines,  122. 

Arsonium  compounds,  122. 
Aseptol,  387. 
Asparagine,  239. 
Aspartic  acid,  239. 
Aspartic  aldehyde,  516. 
Asphalt,  46. 

Asymmetric  carbon  atoms,  31,  32. 
Atoms,  law  of  even  numbers  of,  22. 
Atro-lactinic  acid,  424. 
Atropic  acid,  403,  410,  418. 
Atropine,  490. 
Auramine,  445. 
Aurantia,  355. 
Aurin,  454. 

Avogadro  and  Ampere* s  theory,  10. 
Azimido-benzene,  350. 
Azines,  501. 
Azo-benzene,  351,  368. 
Azo-blue,  441. 
Azo-dyes,  869. 

Azo-dyes  of  the  naphthalene  series,  370, 
465. 

Azo-compounds,  aromatic,  860,  366,  368. 
Azo-diphenyl  blue,  503. 
Azo-naphthalene,  465. 
Azo-phenols,  386. 
Azo-phenyl-ethyl,  368. 
Azo-phenylene,  501. 
Azo-toluenes,  368. 
Azoxy -benzene,  367. 
Azoxy-compounds,  366. 


B 

Barbituric  acid,  279,  282. 
Bassorin,  295. 
Beer,  81. 

Behenic  acid,  147. 

Behenolic  acid,  168. 

Belladonnine,  490. 

Benzal  chloride,  332,  336,  398. 

Benzaldehyde,  305,  359. 

Benzaldehyde-phenyl-hydrazone,  399. 

Benzaldoxime,  399,  406. 

Benzal  violet,  449. 

Benzamide,  401,  413. 

Benzamide-silver,  414. 

Benzanilide,  413. 

Benzene,  303,  328. 

Benzene,  constitution  of,  311,  816. 

Benzene,  formation,  320. 

Benzene,  properties  and  behaviour,  326. 


524 


INDEX. 


Benzene-azo-dimethyl-aniline,  see  Di- 

methyl-amido-azo-benzene. 
Benzene  derivatives,  303. 
Benzene  derivatives,  formation,  820. 
Benzene  derivatives,  isomeric  relations, 

307,  310,  315. 
Benzene-dicarboxylic  acids,  428. 
Benzene-disulphonic  acids,  375. 
Benzene  disulphoxide,  384. 
Benzene  hexabromide,  328. 
Benzene  hexachloride,  312,  328. 
Benzene  hexahydride,  327,  328. 
Benzene  hydrocarbons,  323. 
Benzene  of  crystallization,  447. 
Benzene  sulphonamide,  374. 
Benzene-sulphinic  acid,  375. 
Benzene-sulphinic  ethers,  375. 
Benzene-sulphonic  chloride,  374. 
Benzene-sulphonic  acid,  305,  306,  373. 
Benzene  thio-hydrate,  see  Phenyl  thio- 

hydrate. 

Benzene-tricarboxylic  acids,  402,  430. 
Benzene  trichloride,  332,  336. 
Benzene-trisulphonic  acid,  305,  375. 
Benzhydrol,  442,  444. 
Benzhydrol-benzoic  acids,  442,  445. 
Benzidam,  350. 
Benzidine,  367,  438,  439. 
Benzile,  458. 
Benzilic  acid,  442,  445. 
Benzoic  acid,  305,  307,  410,  412. 
Benzoic  anhydride,  401,  413. 
Benzoic  ethers,  401,  413. 
Benzoin,  458. 

Benzo-nitrile,  305,  363,  374,  402,  415. 
Benzophenone,  442,  444. 
Benzo-purpurin,  441. 
Benzoyl-acetic  acid,  410,  424. 
Benzoyl-acetone,  400. 
Benzoyl-benzoic  acids,  442,  445,  470. 
Benzoyl-carbinol,  401. 
Benzoyl  chloride,  401,  413. 
Benzoyl  cyanide,  413. 
Benzoyl-ecgonine,  501. 
Benzoyl-formic  acid,  410,  424. 
Benzoyl-glycocoll,  see  hippuric  acid. 
Benzoyl-sulphone-imide,  415. 
Benzyl-aceto-acetic  ether,  407. 
Benzyl  alcohol,  305,  336,  395,  397. 
Benzyl-benzoic  acids,  442,  445. 
Benzyl-benzene,  see  Diphenyl-methane. 
Benzyl  chloride,  318,  332,  335. 
Benzyl  cyanide,  415. 
Benzyl  mercaptan,  397. 
Benzylamine,  359,  397. 
Benzylidene-aniline,  345. 
Berberine,  488. 
Berberonic  acid,  488. 
Berlin  blue,  256. 
Betain,  213, 


Biebrich  scarlet,  370,  372. 
Bile,  519. 
Bilifuscin,  519. 
Bilirubin,  519. 
Bismarck  brown,  360,  371. 
Bitter  almond  oil,  305,  398. 
Bitter-almond-oil  green,  448. 
Biuret,  273. 

Blood  colouring  matter,  518. 
Blood  fibrin,  516. 

Boiling  point,  laws  regulating,  26. 

Bone  glue,  517. 

Bone  oil,  480. 

"  Bordeaux"  (dyes),  372. 

Borneol,  510. 

Borneo  camphor,  510. 

Bornyl  chloride,  510. 

Boron  compounds,  125. 

Brain,  519. 

Brandy,  81. 

Brazil  wood,  514. 

Brasilin,  514. 

Brassylic  acid,  228. 

Brilliant  green,  449. 

Brom-aceto-acetic  ether,  321. 

Bromo-acetophenone,  400. 

Bromo-acetyl  bromide,  177. 

Bromo-acetylene,  70. 

Bromanil,  394. 

Bromanilic  acid,  394. 

Bromo-anilines,  352. 

Bromo-anthraquinones,  474. 

Bromo-benzene,  307,  332,  335. 

Bromo-benzoic  acids,  308. 

Bromo-benzyl  bromide,  469,  476. 

Bromo -camphor,  510. 

Bromo-ethyl-benzene,  332. 

Bromo-ethylene,  70. 

Bromoform,  69. 

Bromo-isatin,  433. 

Bromo-naphthalene,  463. 

Bromo-nitro-benzenes,  318,  339,  405. 

Bromo-phenols,  384. 

Bromo-styrenes,  336. 

Bromo-succinic  acids,  235. 

Bromo-toluenes,  335. 

Brucine,  500. 

Butanes,  41. 

Butine,  57. 

Butyric  acid,  159,  160. 
Butyric  ether,  175. 
Butyric  fermentation,  159. 
Butyl-acridine,  498. 
Butyl  alcohols,  84. 
Butyl-benzenes,  323,  331. 
Butyl  bromides,  66. 
Butyl  chlorides,  66. 
Butyl  iodides,  66. 
Butyl-phenol,  380,  380. 
Butylene  diamine,  195. 


INDEX. 


525 


Butylencs,  46,  51,  62. 
Butyrone,  144. 
Butyro-nitrile,  108. 
Butyryl  chloride,  177. 


C 

Cacodyl,  125. 

Cacodyl  compounds,  122,  124,  125. 

Cacodylic  acid,  125. 

Cacodylic  oxide,  124. 

Cadaverin,  516. 

Caffeic  acid,  427. 

Caffeine,  284. 

Caffetannic  acid,  426. 

Cairolin,  496. 

Campechy  wood,  514. 

Camphene,  507. 

Campholene  cyanide,  510. 

Campholenic  acid,  510. 

Camphor,  509. 

Camphoric  acid,  509. 

Camphoronic  acid,  509. 

Camphor-oxime,  510. 

Camphylamine,  510. 

Cane  sugar,  291. 

Cane  sugar  group,  289. 

Cantharidin,  514. 

Caoutschin,  57. 

Caoutchouc,  506,  509. 

Capric  acid,  161. 

Caprilic  acid,  161. 

Caproic  acid,  161. 

Caramel,  291. 

Carbamic  acid,  270. 

Carbamic  chloride,  270. 

Carbamic  compounds,  274. 

Carbamic  ethers,  270. 

Carbamide,  270. 

Carbamines,  109. 

Carbanihde,  341,  358. 

Carbazole,  438,  440. 

Carbimide,  250,  269. 

Carbinol,  77. 

Carbo-cinchomeronic  acid,  488. 
Carbo-di-imide,  264. 
Carbohydrates,  285. 

Carbohydrates,  reaction  with  a-naphthol 

and  sulphuric  acid,  285. 
Carbo-hydrocinnamic  acid,  465. 
Carbo-pyrrolic  acid,  see  Pyrrol-carboxylic 

acid. 

Carbostyril,  418,  492,  496. 
Carbolic  acid,  381. 
Carbon  bisulphide,  275. 
Carbon  oxychloride,  268. 
Carbon  tetra-iodide,  69. 
Carbonic  acid,  derivatives  of,  266. 
Carbonyl  compounds,  274. 


Carbonyl  di-urea,  274. 

Carboxyl  group,  152. 

Carboxylic  acids,  aromatic,  325,  401,  etc. 

Carboxylic  acids,  fatty,  146. 

Carbyl  sulphate,  197. 

Carmine,  284. 

Carmine  red,  514. 

Carminic  acid,  514. 

Cartilage  glue,  517. 

Carvacrol,  377,  388,  509. 

Carvene,  505,  508. 

Carvol,  388. 

Caryophyllin,  510. 

Caseins,  516. 

Catechu-tannic  acid,  426. 
Cedrene,  506. 
Cedriret,  440. 
Celluloid,  293. 
Cellulose,  292. 
Cerebrin,  519. 
Ceresine,  46. 
Cerotene,  46,  52. 
Cerotic  acid,  162,  163. 
Ceryl  alcohol,  86. 
Ceryl  cerotate,  175. 
Cetyl  alcohol,  86. 
Cetyl  bromide,  66. 
Cetyl  iodide,  66. 
Chain  isomerism,  93. 
Chelidonic  acid,  491. 
Chitin,  518. 
Chloral,  137. 
Chloral  alcoliolate,  137. 
Chloral  hydrate,  68,  137. 
Chloranil,  351,  394. 
Chloranilic  acid,  394. 
Chlorhydrins,  192,  200. 
Chlorinated  alcohols,  83. 
Chloro-acetamide,  183. 
Chloro-acetene,  136. 
Chloro-acetic  acids,  168,  172,  211. 
Chloro-acetic  ethers,  175. 
Chloro-aceto-acetic  ether,  227. 
Chloro-acetyl  chloride,  178. 
Chloro-acetylene,  70. 
Chloro- acrylic  acids,  169. 
Chloro-aniline,  352. 
Chloro-anthracenes,  472. 
Chloro-benzene,  305,  332,  335,  363. 
Chloro-benzoic  acid,  402,  414. 
Chloro-benzyl  chloride,  333. 
Chloro-bromo-benzenes,  335. 
Chloro-camphor,  510. 
Chloro-carbonic  acid,  268. 
Chloro-carbonic  ether,  269,  406. 
Chloro-derivatives  of  benzene,  332. 
Chloro-diphenyl,  438,  439. 
Chloro-ethyl-sulphonic  acid,  197. 
Chloroform,  68,  407. 
Chloro-iodo-benzenes,  336, 


526 


INDEX. 


Chloro-isatln,  433. 
Chloro-malonic  ether,  234. 
Chloro-naphthalenes,  463. 
Chloro-nitro-benzenes,  318,  339. 
Chloro -phenols,  382,  384. 
Chloro-phenyl-acetic  acid,  408. 
Chloro-phthalic  acids,  429. 
Chlorophyll,  514. 
Chloro-picrin,  103. 

Chloro-propionic  acids,  168,  169,  172. 

Chloro-pyridine,  480,  482. 

Chloro-quinoline,  480. 

Chloro-quinone,  393. 

Chloro-toluenes,  318,  332,  335. 

Chloro-xylenes,  332. 

Cholesterin,  519. 

Cholestrophane,  282. 

Cholic  acid,  519. 

Choline,  194,  196. 

Chondrin,  517. 

Chondrogene,  517. 

Chromogenes,  24,  356. 

Chrysaniline,  499. 

Chrysazin,  472. 

Chrysazol,  472. 

Chrysene,  477. 

Chrysoidin,  350,  369. 

Chrysoi'dine,  371. 

Chrysoidines,  370. 

Chrysoin,  871. 

Cincho-lepidine,  497. 

Cinchomeronic  acid,  488. 

Cinchona  alkaloids,  500. 

Cinchoninic  acid,  497. 

Cinchonidine,  500. 

Cinchonine,  482,  500. 

Cinene,  507. 

Cineol,  510. 

Cinnamenyl  compounds,  418. 

Cinnamic  acid,  403,  408,  410,  417. 

Cinnamic  alcohol,  397. 

Cinnamic  aldehyde,  399. 

Cinnamon,  oil  of,  399. 

Cinnamyl  compounds,  418. 

Cinnoline  compounds,  498. 

Circular  polarization,  30,  31. 

Citraconic  acid,  236. 

Citrazinic  acid,  247,  482. 

Citrene,  505,  508. 

Citric  acid,  246. 

Citron,  oil  of,  504,  508. 

Classification  of  Organic  compounds,  23. 

Closed  chains  and  rings,  47,  198,  295,  311. 

Cloves,  oil  of,  390. 

Coagulation,  516. 

Cocaine,  501. 

Cocceryl  alcohol,  192. 

Coccerylic  acid,  218. 

Codeine,  499. 

Ccerulein,  457.  ^ 


Coerulin,  457. 

Ccerulignone,  440. 

Collidine,  481,  482,  487. 

CoUidine-dicarboxylic  ether,  482,  484. 

Collodion,  293. 

Collogenes,  517. 

Colophene,  506. 

Colophonium,  506,  512. 

"  Condensation,"  134,  459,  494. 

Condensation  of  ketones,  etc.,  226. 

Condensed  benzene  nuclei,  459  et  seq. 

Colouring  matters,  natural,  614. 

Combustion,  organic,  4. 

Combustion,  heat  of,  30. 

''Congo"  (dye),  440. 

Coniceins,  489. 

Coniferin,  401,  513. 

Coniferyl  alcohol,  401. 

Conic  acid,  218. 

Conine,  489. 

Constitution  of  organic  compounds,  16 

et  seq. 
Conydrine,  489. 
Conylene,  57. 
Conyrine,  486. 
Copper-zinc  couple,  40. 
Coridine,  481. 
Cotarnine,  500. 
Cotton  dyes,  440,  457. 
Creatine,  278. 
Creatinine,  278. 
Creosol,  390. 
Cresol,  377,  387. 
Cresol  ethyl  ether,  862. 
Cresorcin,  390. 
Cresyl-sulphuric  acid,  388. 
Crocein  scarlet,  370. 
Croconic  acid,  296. 
Crotonic  acids,  164,  165. 
Crotonic  aldehyde,  134. 
Crotonylene,  57,  320. 
Cryptidine,  497. 
Crystal  violet,  453. 
Crystalline,  350. 
Cubebene,  506. 
Cumalic  acid,  239,  491. 
Cumaric  acids,  410,  427. 
Cumarin,  409,  427. 
Cumene,  323,  330. 
Cumenols,  377. 
Cumic  acid,  330,  410,  417. 
Cumic  alcohol,  396. 
Cumic  aldehj^'de,  399. 
Cumidine,  341,  359. 
Cumin,  oil  of,  388,  504. 
Cuminol,  399. 
Cupric  ferrocyanide,  255. 
Curcumin,  514. 
Cyamelide,  258. 
Cyan-acetic  acid,  172. 


INDEX. 


527 


Cyanamlde,  264. 
Cyan-etholine,  259. 
Cyanic  acid,  257. 
Cyanic  ether,  258. 
Cyanines,  496. 
Cyanmethine,  108. 
Cyano-benzene,  402. 
Cyano-carbonic  ether,  223. 
Cyano-diphenyl,  438. 
Cyano-fatty  acids,  171. 
Cyano-naphthalenes,  465. 
Cyano-pyridine,  486. 
Cyano-quinoline,  496. 
Cyanogen,  248,  249. 
Cyanogen  bromide,  257. 
Cyanogen  chloride,  257. 
Cyanogen  compounds,  248,  250. 
Cyanogen  iodide,  257. 
Cyanogen  sulphide,  262. 
Cyanol,  350. 
Cyanuramide,  265. 
Cyanuric  acid,  259. 
Cyanuric  chloride,  257. 
Cymene,  323,  325,  331. 
Cymidine,  359. 
Cymogene,  44. 
Cystine,  224, 
Cyste'in,  224. 


D 

Dambose,  289, 
Daphnetin,  428. 
Daphnin,  428. 
Decane,  44. 

Decomposition  of  hydrocarbons,  45. 
Decomposition  of  optically  active  com- 
pounds by  ferments,  31. 
Decyl  alcohols,  86. 
Desmotropism,  266,  430. 
Desoxalic  acid,  247. 
Desoxy-benzoin,  458. 
Developer,  photographic,  391. 
Dextrine,  294. 
Dextro- tartaric  acid,  240. 
Dextrose,  286,  288. 
Diacetamide,  180. 
Diacetin,  202. 
Diaceto-acetic  ether,  227. 
Diaceto-succinic  ether,  227. 
Diacetyl,  221,  322. 
Diacetylene,  58. 

Diacetylene-dicarboxylic  acid,  68,  238. 

Diacetylene-monocarboxylic  acid,  168. 

Di-allyl,  57. 

Dialuric  acid,  279,  282. 

Diamide,  117. 

Diamido-azo-benzene,  369,  371. 
Diamido-benzenes,  314. 


Diamido-benzoic  acids,  314,  414. 
Diamido-benzophenone,  444. 
Diamido-diphenyl,  439. 
Diamido-diphenylamine,  341,  356. 
Diamido-phcnols,  386. 
Diamido-plienyl-acridine,  355. 
Diamido-stilbene,  457. 
Diamido-triphenyl-methane,  449. 
Diamines,  193. 

Diamines,  aromatic,  349,  359. 
Diastase,  294. 
Diazo-acetic  ether,  213. 
Diazo-amido-benzene,  366. 
Diazo-amido-compounds,  364,  365. 
Diazo-amido-naphthalene,  465. 
Diazo-amido-toluene,  371. 
Diazo-benzene,  361,  364. 
Diazo-benzene  imide,  364. 
Diazo-benzene  nitrate,  364. 
Diazo-benzene  perbromide,  364. 
Diazo-benzene-potassium  oxide,  364. 
Diazo-benzene-potassium  sulphite,  372. 
Diazo-benzene-silver  oxide,  364. 
Diazo-benzene-sulphonic  acid,  375. 
Diazo-benzoic  acids,  414. 
Diazo-cinnamic  acids,  418. 
Diazo-compounds,  aromatic,  346,  360. 
Diazo-compounds,  fatty,  118. 
Diazo-ethane-sulphonic  acid,  118. 
Diazo-ethoxane,  103. 
Diazo-phenols,  386. 
Diazotising,  361. 
Dibenzoyl-acetic  acid,  459. 
Dibenzoyl-methane,  459. 
Dibenzyl,  437,  457. 
Dibromo-anthracenes,  472. 
Dibromo-acrolein,  138. 
Dibromo-benzenes,  314,  332,  335. 
Dibromo-indigo,  432. 
Dibromo-propionic  acids,  170. 
Dibromo-pyridine,  500. 
Dibromo-succinic  acid,  235,  243. 
Dibromo-w-xylene,  331. 
Dicetyl-ether,  92. 
Dicetyl-malonic  acid,  228. 
Dichloro-acetic  acid,  172. 
Dichloro-aceto-acetic  ether,  227. 
Dichloro-acetone,  247. 
Dichloro-aldehyde,  137. 
Dichloro-anthraquinone,  474. 
Dichloro-benzenes,  305,  332,  335. 
Dichloro-diphenyl,  438. 
Dichloro-indigo,  432. 
Dichloro-tetroxy-benzene,  392. 
Dichloro-toluenes,  332,  333. 
Dicyan-diamide,  250,  264. 
Dicyano-benzenes,  375. 
Dicyano-diphenyl,  438. 
Diethyl,  see  Normal  Butane. 
Diethylamine,  117. 


528 


INDEX. 


Diethyl-aniline,  341. 
Diethyl-benzenes,  323. 
Diethyl  disulphide,  95. 
Diethyl  ether,  91. 
Diethyl-glycol,  192. 
Diethyl-hydrazine,  118. 
Diethyl-hydrazine,  urea  derivatives  of, 
118. 

Diethyl-indigo,  432. 
Diethyl  ketone,  144. 
Diethyl-phosphinic  acid,  121. 
Diethyl  sulphide,  94. 
Diethyl  sulphone,  96. 
Diethyl  sulphoxide,  90. 
Diethyl-toluidine,  436. 
Diethyl-urea,  270. 
Diethylene-diamine,  195. 
Digallic  acid,  see  Tannin. 
DiglycoUamic  acid,  212. 
Dihydro-collidine-dicarboxylic  ether,  482. 
Dihydro-methyl-pyridine,  485, 
Dihydro-phthalic  acid,  428. 
Dihydro-pyridine,  488. 
Dihydro-quinoline,  496. 
Di-iodo-benzenes,  332. 
Di-isocyanic  acid,  260. 
Diketo-butane,  221. 
Diketo-hexane,  221. 
Diketones,  221,  222,  400. 
Dill,  oil  of,  508. 
Dimethyl-acetamide,  180. 
Dimethyl-aceto-acetic  ether,  226. 
Dimethyl-alloxan,  282. 
Dimethyl-amido-azo-benzene,  363,  371. 
Dimethyl-amido-azobenzene-sulphonic 

acid,  371, 
Dimethylamine,  116. 
Dimethyl-aniline,  341,  354. 
Dimethyl-anthracenes,  472,  475. 
Dimethyl-arsine  compounds,  122,  124. 
Dimethyl-benzenes,  see  Xylene. 
Dimethyl-benzoic  acids,  416. 
Dimethyl-conine,  489. 
Dimethyl  ether,  92. 
Dimethyl-ethyl-benzenes,  323. 
Dimethyl-furfurane,  297,  300. 
Dimethyl  ketone,  141,  143. 
Dimethyl-malonic  acid,  234. 
Dimethyl-naphthalenes,  467. 
Dimethyl-naphthylamines,  465. 
Dimethyl-nitrosamine,  115. 
Dimethyl-oxamic  ether,  113,  233. 
Dimethyl-parabanic  acid,  282. 
Dimethyl-phenylene  green,  356. 
Dimethyl -phosphine,  120. 
Dimethyl-phosphinic  acid,  120. 
Dimethyl-piperidine,  489. 
Dimethyl-pyridine,  480,  487. 
Dimethyl-pyridine-carboxylic  ether,  483. 
Dimethyl-pyrrol,  297, 


Dimethyl-quinolines,  480. 
Dimethyl  sulphide,  93. 
Dimethyl-thiazol,  302. 
Dimethyl-thiophene,  297. 
Dimethyl-toluidine,  359. 
Dimethyl-uric  acid,  283. 
Dinaphthols,  466. 
Dinaphthyl,  468. 
Dinicotinic  acid,  488. 
Dinitranilines,  353. 
Dinitro-benzenes,  305,  337,  338. 
Dinitro-cresol,  388. 
Dinitro-diphenyl,  438,  439. 
Dinitro-diphenyl-diacetylene,  459. 
Dinitro-diphenylamines,  355. 
Dinitro-ethane,  103. 
Dinitro-naphthol,  466. 
Dinitro-naphthol-sulphonic  acid,  466. 
Dinitro-phenols,  305,  338,  385. 
Dinitro-toluenes,  316,  337,  338. 
'*  Dioses,"  290. 
Dioxindole,  434. 
Dioxy-acids,  165,  204. 
Dioxy-anthracenes,  472,  473. 
Dioxy-anthraquinones,  472. 
Dioxy-azobenzene-sulphonic  acid,  371. 
Dioxy-benzenes,  375,  388, 
Dioxy-benzoic  acids,  425. 
Dioxy-benzophenone,  445. 
Dioxy-cinnamic  acids,  427. 
Dioxy-diphenylamine,  357. 
Dioxy-diphenyl-phthalide,  455. 
Dioxy-diquinoyl,  395. 
Dioxy-naphthalenes,  467. 
Dioxy-quinone,  395. 
Dioxy-tartaric  acid,  243,  244,  322. 
Dioxy-terephthalic  acid,  429. 
Dioxy-xylenes,  390. 
Dipentene,  506,  507. 
Dipentene  dihydrochloride,  508. 
Dipentene  tetrabromide,  508. 
Diphenols,  438,  440. 
Diphenyl,  438. 

Diphenyl-acetic  acid,  442,  445. 
Diphenyl-acetylene,  457. 
Diphenyl-benzene,  438,  441. 
Diphenyl-bromo-ethane,  444. 
Diphenyl-carbinol,  see  Benzhydrol. 
Diphenyl-carboxylic  acid,  438. 
Diphenyl-diacetylene,  459. 
Diphenyl-dicarboxylic  acid,  438,  441. 
Diphenyl-ethane,  442,  445,  457. 
Diphenyl-ethylene,  457. 
Diphenyl-glycollic  acid,  445. 
Diphenyl  group,  438 . 
Di phenyl-hydrazine,  373. 
Diphenyl  ketone,  444. 
Diphenyl-methane,  437,  442,  444. 
Diphenyl-nitrosamine,  355 
Diphenyl  oxide,  382, 


INDEX. 


529 


Diphenyl-phthalide,  455. 
Diphenyl-succinic  acid,  458. 
Diphenyl-tolyl-methane,  446,  447. 
Diphenyl-thio-nrea,  358. 
Diphenyl-urea,  351,  358. 
Diphenylamine,  341,  355. 
Diphenylamine  blue,  355,  453. 
Diphenylene  ketone,  442. 
Diphenylene-methane,  446. 
Diphenylene  oxide,  438,  440. 
Diphenyline,  438,  440. 
Diphenylol,  438. 
Dipicolinic  acid,  488. 
Dipiperidyl,  490. 
Dipropargyl,  58. 
Dipyridine,  480,  485. 
Dipyridyl,  480,  485. 
Diquinoline,  480,  496. 
Diquinolyline,  480,  496. 
Disazo- compounds,  370. 
Distillation,  fractional,  27,  81. 
Disulphanilic  acid,  375. 
Dithio-acids,  179. 
Dithio-carbamic  acid,  276. 
Dithio-dicyanic  acid,  263. 
Dithio-urethane,  276. 
Ditolylamine,  359. 
Ditolyls,  438. 
Dodecane,  34. 
Double  bond,  49,  50. 
Dulcite,  204. 
Durene,  323,  331. 
Durenols,  377. 
Dyes,  376,  514,  etc. 
Dynamite,  202. 


E 

Ecgonine,  501. 

Egg  albumen,  516. 

Egg,  white  of,  515. 

Elseoptenes,  504. 

Elaidic.acid,  167. 

Elastin,  518. 

Elayl,  see  ethylene. 

Electrolysis,  39,  49. 

Empirical  formulae,  7. 

Emulsin,  294,  398. 

Eosins,  455. 

Epichlorhydrin,  201. 

Erigeron,  oil  of,  508. 

Erucic  acid,  167. 

Erythrin,  203,  425. 

Erythrite,  203. 

Erythritic  acid,  219. 

Erythro-oxy-anthraquinone,  472,  474. 

Erythrosin,  456. 

Etard  reaction,  the,  398. 

Ethal,  86. 

(506) 


Ethane,  16,  40. 

Ethane-tricarboxylic  acid,  245. 
Ethenyl-amidine,  185,  349. 
Ethenyl-amidoxime,  187. 
Ethenyl-diphenyl-amidine,  185. 
Ethenyl-triethyl  ether,  199. 
Ethereal  oils,  504. 
Ether-acids,  98. 
Ethers,  simple,  88. 
Ethers,  compound,  70,  97,  173. 
Ethers  of  the  fatty  acids,  173. 
Ethidene  chloride,  68. 
Ethionic  acid,  197. 
Ethyl-acetamide,  180,  181. 
Ethyl-aceto-acetic  ether,  226. 
Ethyl-acetamido  chloride,  183. 
Ethyl-acetimido  chloride,  183. 
Ethyl  alcohol,  79. 
Ethyl-amine,  117. 
Ethyl-aniline,  341. 
Ethyl-benzene,  318,  323,  329. 
Ethyl-benzhydroxamic  acid,  187. 
Ethyl-benzoic  acids,  416. 
Ethyl  bromide,  64. 
Ethyl-camphor,  510. 
Ethyl-carbamine,  110. 
Ethyl-carbonic  acid,  268. 
Ethyl-cetyl  ether,  92. 
Ethyl  chloride,  64. 
Ethyl  cyanamide,  264. 
Ethyl  cyanide,  108. 

Ethyl-dithiocarbamic  acid  compounds, 
276. 

Ethyl-glycollic  acid,  211. 

Ethyl-giycoUic  acid,  derivatives  of,  211. 

Ethyl-hydrazine,  118. 

Ethyl  hydride,  40. 

Ethyl  hydrosulphide,  93  et  seq. 

Ethyl-indoxyl,  435. 

Ethyl  iodide,  65. 

Ethyl  isocyanide,  110. 

Ethyl  isothiocyanate,  263. 

Ethyl-lactic  acid,  216. 

Ethyl-malonic  ethers,  234. 

Ethyl-methyl-pyridine,  486. 

Ethyl  nitrate,  99. 

Ethyl  nitrite,  100. 

Ethyl-nitrogen  chloride,  117. 

Ethyl-nitrolic  acid,  102. 

Ethyl-oxalic  acid,  232. 

Ethyl-oxalyl  chloride,  232. 

Ethyl-oxanthranol,  472. 

Ethyl-phenol,  380,  388. 

Ethyl-phosphines,  120,  121. 

Ethyl-piperidine,  489. 

Ethyl-pyridine,  486. 

Ethyl-salicylic  acid,  421. 

Ethyl  sulphide,  93. 

Ethyl-sulphinic  acid,  105. 

Ethyl-sulphonic  acid,  105. 

2L 


530 


INDEX. 


Ethyl-sulphonic  chloride,  105. 
Ethyl-sulphonic  ether,  106. 
Ethyl-sulphuric  acid,  104. 
Ethyl-sulphurous  acid,  105. 
Ethyl-toluenes,  330. 
Ethyl-urea,  272. 
Ethylene,  46,  50. 
Ethylene  bromide,  67. 
Ethylene  chloride,  61,  67. 
Ethylene  cyanhydrin,  193,  207. 
Ethylene  cyanide,  192. 
Ethylene  diamine,  188,  195. 
Ethylene-disulphonic  acid,  106. 
Ethylene  glycol,  191. 
Ethylene  hydramine,  194. 
Ethylene-imine,  194. 
Ethylene  iodide,  67. 
Ethylene-lactic  acid,  216. 
Ethylene  oxide,  193. 
Ethylidene  chloride,  61,  68. 
Ethylidene  cyanhydrin,  133,  193,  207. 
Ethylidene-diphenyl  diamine,  345. 
Ethylidene-disulphonic  acid,  106. 
Ethylidene  glycol,  131,  191. 
Ethylidene-lactic  acid,  214. 
Ethylidene -succinic  acid,  235. 
Eugenol,  390. 
Eupion,  46. 
Eupittone,  454. 
Eurhodines,  502. 


F 

Fast  yellow,  369. 
Fast  red,  466. 
Fats,  162. 

Fatty  acid  series,  146. 
Fehling's  solution,  241. 
Fermentation,  80. 
Ferments,  293. 
Fernambuco  wood,  514. 
Ferulic  acid,  427. 
Fibrins,  516. 
Fibrogene,  517. 
Fibrino -plastic  substance, 
Fiddle  resin,  500. 
Fittig  reaction,  the,  324. 
Flavaniline,  497. 
Flavean  hydride,  252. 
Flavol,  472. 

Flavo-purpurin,  472,  475. 
Fluo-benzene,  335. 
Fluoranthene,  477. 
Fluorene,  442,  446. 
Fluorenyl  alcohol,  442. 
Fluorescein,  456. 
Fluorescin,  456. 
Formamide,  183. 
Formic  acid,  154. 


Formic  aldehyde,  135. 
Formic  ether,  175. 
Formose,  286. 
Formulae,  rational,  19. 
Formulae,  constitutional,  16. 
Formyl,  153. 
Formyl. acetic  acid,  222. 
Formyl-acetic  ether,  321. 
Formyl-diphenylamine,  498. 
Formyl-trisulphonic  acid,  198. 
Fruit  ethers,  175. 
Fruit  sugar,  288. 
Fuchsine,  351,  451. 
Fumaric  acid,  236,  237. 
Furfurane,  297,  299. 
Furfurane  alcohol,  297,  300. 
Furfurane  compounds,  300. 
Furfurol,  297,  300. 
Fusel  oil,  80. 


G 

Galactose,  288. 
Galipot  resin,  512. 
Gallein,  456. 
Galline,  456. 

Gallic  acid,  391,  411,  425. 
Gallofiavin,  475. 
Gallo-tannic  acid,  426. 
Garlic,  oil  of,  97. 
Garnet  brown  (dye),  386. 
Gasoline,  44. 
Gelatine,  517. 
Globulins,  517. 
Gluconic  acid,  219. 
Glucosamines  287,  289. 
Glucoses,  285,  286. 
Glucosides,  426,  512. 
Glue,  517. 
Glutamic  acid,  240. 
Glutaric  acid,  235. 
Glutazine,  486. 
Glutin,  517. 

Glyceramic  acid,  see  Serine. 
Glyceric  acid,  219. 
Glyceric  aldehyde,  220. 
Glycerides,  162,  163,  202. 
Glycerine,  199. 
Glycerine  nitrate,  201. 
Glycerine-phosphoric  acid,  200. 
Glycerine-sulphuric  acid,  200. 
Glyceryl  chloride,  69. 
Glycide  alcohol,  201. 
Glycide  compounds,  201. 
Glycocholic  acid,  212,  519. 
Glycocoll,  211,  212. 
Glycocoll-amide,  211. 
Glycocyamine,  278. 
Glycocyamidine,  278, 


INDEX. 


531 


Glycogen,  294. 

GlycoUamide,  211. 

Glycol  bromhydrins,  192. 

Glycol  chlorhydrins,  188,  192. 

Glycol,  ethers  of,  192. 

Glycol  mercaptan,  etc.,  193. 

Glycollic  acetate,  188,  192. 

Glycollic  acid,  170,  210. 

Glycollic  aldehyde,  220. 

Glycollic  anhydride,  212. 

Glycollic  chloride,  211. 

Glycollic  ether,  211. 

Glycolide,  212. 

Glycols,  187. 

Glycuronic  acid,  244. 

Glyoxal,  221. 

Gly oxalic  acid,  222. 

Glyoxaline,  221. 

Granulose,  293, 

Grape  sugar,  288. 

Griess  reaction,  the,  363. 

Guaiacol,  389. 

Guanidine,  277. 

Guanine,  281,  284. 

Gums,  294. 

Gum  benzoin,  412. 

Gum  lac,  512. 

Gun  cotton,  293. 

Guttapercha,  509. 


H 

Hsematin,  618. 
Hsematoxylin,  514. 
Hsemin,  518. 
Haemoglobin,  518. 

Halogen  derivatives  of  the  aromatic  series, 
332. 

Halogen  derivatives  of  the  fatty  series, 
58. 

Harmin,  514. 
Harmalin,  514. 
Heat  of  formation,  30. 
Helianthin,  360,  371. 
Helicin,  513. 
Hemellithene,  323,  330. 
Hemi-albumoses,  516. 
Hemi-mellitic  acid,  305,  430. 
Hemipinic  acid,  430. 
Hemiterpenes,  506. 
Heptanes,  44. 
Heptyl  alcohols,  86. 
Heptylene,  46. 
Hesperidin,  513. 
Hesperidene,  505,  508. 
Hexabromo-benzene,  321,  335. 
Hexachloro-benzenc,  332,  335. 
Hexachloro-ethane,  60. 
Hexa-decane,  34. 


Hexadecyl  alcohol,  86. 
Hex-ethyl-benzene,  323. 
Hexahydro-bcnzene,  312,  322. 
Hexahydro-dipyridyl,  490. 
Hexahydro-pyridinc,  479. 
Hexahydro-tercphthalic  acid,  312,  429. 
Hexamethyl-benzene,  320,  323,  331. 
Hexa-methylene,  52,  312. 
Hexamethyl-triamido-triphenyl-methane 
452. 

Hexamethyl-rosaniline,  452,  453. 
Hexanitro-diphenylamine,  355. 
Hexoxy-anthraquinone,  474. 
Hexoxy-benzene,  322,  377,  392. 
Hexoxy-diphenyl,  440. 
Hexagon  formula,  312. 
Hexanes,  44. 
Hexine,  57. 
Hexyl  alcohols,  86. 
Hexyl  chloride,  66. 
Hexyl  iodide,  321. 
Hexylene,  46. 
Hippuric  acid,  212,  414. 
Homatropine,  490. 
Homoconic  acid,  218. 
Homo-pyrocatechin,  377,  390. 
Homologous  series,  20. 
Homology,  20. 
Honey  stone,  431. 
Horn  substance,  518. 
Hydantoic  acid,  273. 
Hydantoin,  273. 
Hydracrylic  acid,  216. 
Hydramines,  194. 
Hydratropic  acid,  410,  417. 
Hydrazides,  135. 
Hydrazine,  117. 

Hydrazines,  aromatic,  362,  372. 
Hydrazines,  fatty,  117. 
Hydrazo-benzene,  367. 
Hydrazo-compounds,  119,  367. 
Hydrazones,  135,  143,  287,  373. 
Hydrindic  acid,  423. 
Hydro-acridine,  479. 
Hydro-anthranol,  472,  473. 
Hydro-benzamide,  398. 
Hydro-benzoin,  458. 
Hydro-benzoin  acetic  ether,  458. 
Hydrocarbons,  aromatic,  323. 
Hydrocarbons,  fatty,  34. 
Hydro-carbostyril,  417,  492. 
Hydrocinnamic  acid,  408,  410,  417. 
Hydro-coerulignone,  441. 
Hydro-collidine-dicarboxylic  ether,  482, 
484. 

Hydrocumaric  acid,  408,  410. 
Hydrocyanic  acid,  252. 
Hydro-ferricyanic  acid,  256. 
Hydro-ferrocyanic  acid,  255. 
Hydro-mellitic  acid,  431, 


532 


INDEX. 


Hydro-muconic  acid,  236. 
Hydronaphthalene-tetracarboxylic  ether, 
461. 

Hydro-naphthoquinones,  467. 
Hydro-paracumaric  acid,  408,  410. 
Hydro-phenazine,  360,  502. 
Hydroquinone,  389. 
Hydroquinone-dicarboxylic  acid,  429. 
Hydroquinone-tetracarboxylic  acid,  430. 
Hydrosulphides,  93. 
Hydroxamic  acids,  187. 
Hyoscine,  490. 
Hyoscyamine,  490. 
Hypogseic  acid,  164. 
Hypoxanthine,  284. 
Hypochlorous  ether,  103. 


I 

Imesatin,  433. 
Imides,  111,  231. 

Imido-carbamic  compounds,  274,  277. 

Imido-carbonic  acid,  269. 

Tmido-carbonic  compounds,  274. 

Imido-carbonic  ether,  269. 

Imido-chlorides,  183. 

Imido-ethers,  184. 

Imido-thio-ethers,  184. 

Imines,  194,  300. 

Indamines,  356. 

Indene,  468. 

Indican,  431. 

Indicator,  371. 

Indigo,  399,  431. 

Indigo-brown,  431. 

Indigo-gelatine,  431. 

Indigo-purpurin,  432. 

Indigo-red,  431. 

Indigo-sulphonic  acids,  432. 

Indigo-white,  432. 

Indin,  432. 

Indirubin,  432. 

Indole,  433,  436. 

Indonaphthene,  468. 

Indophenin,  301. 

Indophenols,  356. 

Indoxyl,  433,  435. 

Indoxyl-sulphuric  acid,  435. 

Indoxylic  acid,  435. 

Indoxylic  ether,  435. 

Indulines,  503. 

Inosite,  289. 

Inulin,  294. 

lodo-benzene,  332,  363. 

lodo-propiolic  acid,  169. 

lodo-propionic  acids,  170,  172. 

Iodoform,  69. 

Iodoform  reaction,  the,  83. 

lodol,  300. 


Iridoline,  497. 

Isatic  acid,  424. 

Isatin,  424,  433. 

Isatin  chloride,  434, 

Isatoic  acid,  434. 

Isatoxime,  434. 

Isethionic  acid,  197. 

Iso-anthraflavic  acid,  472. 

Isbbutyric  acid,  160.  . 

Isobutyl  alcohol,  85. 

Iso-cinchomeronic  acid,  488. 

Iso-citric  acid,  247. 

Iso-crotonic  acid,  166. 

Isocyanic  ethers,  258. 

Isocyanides,  109,  405. 

Isocyanuric  ethers,  269. 

Iso-cymenes,  331. 

Iso-cymidine,  359. 

Iso-dipyridyl,  490. 

Iso-durene,  323. 

Iso-ferulic  acid,  513. 

Iso-hydrobenzoin,  458. 

Iso-melamine,  265. 

Isomerism,  12,  16,  41,  92,  208. 

Isomerism  in  the  cyanogen  group,  265. 

Isomerism  of  the  benzene  derivatives, 

307,  318. 
Isomerism  of  position,  93,  317. 
Iso-nicotine,  490. 
Iso-nicotinic  acid,  487. 
Iso-nitrile  reaction,  the,  114. 
Iso-nitriles,  109. 
Iso-nitroso-acetone,  143, 
Iso-nitroso-ketones,  143. 
Iso-nitroso-methyl-acetone,  221. 
Iso-nitroso-naphthols,  467. 
Iso-paraflSns,  43. 
Isophthalic  acid,  429. 
Isoprene,  57,  608. 
Isopropyl  alcohol,  84. 
tsopropyl-benzene,  323,  330. 
tsopropyl-benzoic  acid,  417. 
Isopropyl  chloride,  65. 
Isopropyl  iodide,  65. 
Isopropyl-piperidine,  489. 
[so-propyl-pyridine,  486. 
[so-purpuric  acid,  386. 
[so-saccharic  acid,  219,  244. 
[so-succinic  acid,  235. 
[so-tropine,  490. 
[so-xylene,  329. 
[suret,  187. 
[taconic  acid,  236. 


J 

Japan  camphor,  509. 
Juglone,  467. 
Juniper,  oil  of,  506. 


INT)EX. 


533 


K 

Keratrin,  518. 
Ketines,  491. 
Keto-compounds,  140. 
Keto-dihydro-pyridine,  486. 
Keto-propionic  acid,  223. 
Keto-tetrahydro-cymene,  511. 
Ketone-acids,  aromatic,  402. 
Ketone-acids,  fatty,  222. 
Ketone-acids,  decomposition  of,  225. 
Ketone-aldehydes,  143,  222. 
Ketone-alcohols,  205,  221,  286,  400. 
Ketones,  aromatic,  399. 
Ketones,  fatty,  128,  138. 
Ketones,  mixed,  139. 
Kino-tannic  acid,  426. 


L. 

Lactames,  416. 

Lactic  acids,  214  to  216. 

Lactic  acids,  derivatives  of,  216. 

Lactic  fermentation,  214. 

Lactide,  215,  216. 

Lactimes,  416. 

Lactones,  218. 

Lactose,  288. 

Lactyl  chloride,  178,  216. 

Lactyl-urea,  273. 

Lsevo-conine,  489. 

Lsevo-tartaric  acid,  242. 

Lsevulose,  286,  288. 

Lakes,  474. 

Laurie  acid,  161. 

Laurone,  144. 

Lauth's  violet,  356. 

Lead  acetates,  158. 

Lead,  sugar  of,  158. 

Lead  tetra-methide,  128. 

Leather,  517. 

Lecithin,  519. 

Legumin,  517. 

Lekene,  46. 

Lepargylic  acid,  228. 

Lepidine,  497. 

Leucaniline,  450. 

Leucaurin,  454. 

Leucic  acid,  217. 

Leucine,  217. 

Leuco-bases,  448. 

Leuco-compounds,  448. 

Leuco-malachite  green,  354,  449. 

Leuco-rosolic  acid,  454. 

Leuco-thionine,  356. 

Leuconic  acid,  296. 

Levulinic  acid,  227. 

Lichen  acids,  425. 

Lichenin,  294. 


"  Life  force,"  1. 

Liebermann  reaction,  the,  354,  380. 

Light  blue,  453. 

Light  green,  453. 

Lignoceric  acid,  147. 

Ligroin,  44. 

Limonene,  508. 

Linking,  double,  49,  403. 

Linking,  triple,  55. 

Linoleic  acid,  167. 

Litmus,  390,  514. 

Logwood,  514. 

Lupetidines,  489. 

Lutidines,  480,  481,  487. 

Lutidinic  acid,  488. 


M 

m  =  meta,  see  Meta-compounds. 

Madder  root,  474. 

Magdala  red,  503. 

Malachite  green,  449. 

Malamic  acid,  239. 

Malamide,  239. 

Maleic  acid,  236,  237. 

Malic  acid,  238. 

Malonic  acid,  233. 

Malonic  aldehyde-acid,  409. 

Malonic  ether,  233. 

Malonic  ether  synthesis,  234,  407. 

"  Malonyl,"  229. 

Malonyl-urea,  282. 

Maltose,  291. 

Mandelic  acid,  402,  408,  428. 
Mannide,  204. 
Mannitan,  204. 
Mannite,  203. 
Mannitic  acid,  219. 
Mannose,  204,  289. 
Margaric  acid,  163. 
Marsh  gas,  39. 
Martins'  yellow,  466. 
Mauveine,  503. 
Meconic  acid,  491. 
Meconine,  500. 
Meconinic  acid,  430. 
Melamine,  265. 
Melene,  46,  52. 

Melilotic  acid,  see  o-Cumaric  acid. 

Melissic  acid,  147,  163. 

Melissic  alcohol,  86. 

Melitose,  292. 

Mellitene,  331. 

Mellitic  acid,  322,  402,  431. 

Mellophanic  acid,  430. 

Melting  point,  rules  regulating,  28. 

Mendius'  reaction,  the,  113,  182. 

Menthol,  510. 

Mercaptals,  132. 


534 


INDEX. 


Mercaptan,  93  et  seq. 
Mercurialin,  116. 
Mercuric  cyanide,  254. 
Mercury  diphenyl,  339. 
Mercury  ethide,  127. 
Mercury-ethyl  hydroxide,  128. 
Mercury,  fulminate  of,  108. 
Mercury  methide,  127. 
Mercury-methyl  chloride,  128. 
Mesaconic  acid,  236. 
Mesidine,  343,  359. 
Mesityl  oxide,  142,  144. 
Mesitylene,  142,  320,  330. 
Mesitylene,  constitution  of,  315. 
Mesitylene  hexahydride,  330. 
Mesitylenic  acid,  416. 
Meso-paraffins,  43. 
Mesorcin,  377,  390. 
Meso-tartaric  acid,  242. 
Mesoxalic  acid,  244. 
Metacyl  chloride,  144. 
Meta-compounds,  see  individually. 
Metaldehyde,  136. 
Metallic  cyanides,  254  et  seq. 
Metamerism,  93,  319. 
Metanil  yellow,  375. 
Metanilic  acid,  375. 
Meta-styrene,  332. 
Methacrylic  acid,  166. 
Methane,  39. 

Methane-di-  and  tri-carboxylic  acids,  233, 
245. 

Methane  di-  and  tri-sulphonio  acids,  106. 
Methane  series,  34. 
Methyl-amido-phenol,  386. 
Methenyl-amido-thiophenol,  386. 
Methenyl-amidoxime,  187. 
Methionic  acid,  196. 
Methoxy-pyridine,  486. 
Methoxy-quinoline.  496. 
Methyl-acetanilide,  341. 
Methyl-aceto-acetic  ether,  226. 
Methyl-acridine,  498. 
Methyl  alcohol,  78. 
Methyl  aldehyde,  135. 
Methyl-alloxan,  282. 
Methyl-amine,  116. 
Methyl-amyl  ether,  90. 
Methyl-aniline,  341,  353. 
Methyl-anthracenes,  472,  475. 
Methyl-anthraquinone,  475. 
Methyl-arsenic  compounds,  122  et  seq. 
Methyl-benzene,  see  Toluene. 
Methyl  bromide,  64. 
Methyl-carbostyril,  493. 
Methyl-carbamine,  110. 
Methyl  chloride,  64. 
Methyl-chloroform,  69. 
Methyl-conine,  489. 
Methyl-cumarin,  408. 


Methyl-cyanamide,  260. 
Methyl  cyanide,  108. 
Methyl-diphenylamine,  347,  355. 
Methyl  ether,  17,  92. 
Methyl-ethyl-acetic  acid,  161. 
Methyl-ethyl-aceto-acetic  ether,  226. 
Methyl-ethylamine,  114. 
Methyl-ethyl-benzenes,  323,  330. 
Methyl-ethyl-benzoic  acids,  412. 
Methyl-ethyl-carbin-carbinol,  86. 
Methyl-ethyl-carbinol,  84. 
Methyl-ethyl  ether,  89. 
Methyl-ethyl  ketone,  138,  320. 
Methyl-ethyl  sulphide,  95. 
Methyl-furfurane,  297,  300. 
Methyl  green,  453. 
Methyl-hydantoin,  273. 
Methyl-hydroquinone,  513. 
Methyl  hydrosulphide,  93  et  seq. 
Methyl-imesatin,  434. 
Methyl-indole,  437. 
Methyl  iodide,  64. 
Methyl-isatin,  434. 
Methyl-isatic  acid,  484. 
Methyl  isocyanide,  110. 
Methyl  iso-thiacetanilide,  185. 
Methyl  isothiocyanate,  263. 
Methyl-ketole,  436. 
Methyl-morphine,  499. 
Methyl-naphthalenes,  467. 
Methyl-naphthylamines,  465. 
Methyl  nitrate,  99. 
Methyl  nitrite,  100. 
Methyl-nonyl  ketone,  144. 
Methyl  orange,  371. 
Methyl-oxamic  ether,  113. 
Methyl-oxy-quinoline,  493. 
Methyl-parabanic  acid,  282. 
Methyl-phosphine,  121. 
Methyl-phenazine,  502. 
Methyl-piperidines,  489. 
Methyl-propyl-benzenes,  331. 
Methyl-pseudo-isatin,  434. 
Methyl-pyridines,  480,  486- 
Methyl-pyridone,  486. 
Methyl-pyrogallol,  377. 
Methyl-pyrrol,  297. 
Methyl-quinoline,  480,  492,  496. 
Methyl  sulphide,  93  et  seq. 
Methyl-sulphonic  acid,  105. 
Methyl-sulphuric  acid,  104. 
Methyl-thio-carbimide,  275. 
Methyl-thiophenes,  297,  299. 
Methyl-toluidines,  342,  359. 
Methyl-uracyl,  273. 
Methyl-urea,  272. 
Methyl-uric  acid,  283. 
Methyl  violets,  354,  452. 
Methylal,  136. 
"Methylene,"  46,  60. 


INDEX. 


535 


Methylene  bromide,  66. 

Methylene  bhie,  356,  360. 

Methylene  chloride,  66. 

Methylene  glycol,  191. 

Methylene  iodide,  66. 

Methylenitan,  286. 

Mint  camphor,  510. 

Milk  sugar,  291. 

Milton's  reagent,  515. 

Molecular  rearrangements,  166,  309. 

Molecular  refraction  equivalent,  30. 

Molecular  weight,  determination  of,  8. 

Molecular  volume,  25. 

Mono-compounds,  see  individually. 

Monocliloro-acetone,  144. 

Monochloro -aldehyde,  137. 

Mono-ethylin,  200. 

Monoformin,  154,  202. 

Mordants,  475. 

Morintannic  acid,  426. 

Morphine,  499. 

Moss  starch,  294. 

Mucic  acid,  243,  244. 

Mucilage,  295,  518. 

Mucin,  518. 

Murexide,  283. 

Muscle  albumen,  517. 

Mustard  oils,  262. 

Mustard  oil  reaction,  the,  114. 

Myosin,  517. 

Myricyl  alcohol,  72,  86. 

Myristic  acid,  161. 

Myristone,  144. 

Myronic  acid,  513. 

Myrosin,  513. 


N 

Naphtha,  see  Petroleum  ether. 
Naphthalene,  428,  460. 
Naphthalene,  constitution  of,  463. 
Naphthalene-dicarboxylic  acids,  468. 
Naphthalene  dichloride,  462. 
Naphthalene  hydrides,  462. 
Naphthalene-sulphonic  acids,  465. 
Naphthalene  tetrachloride,  462. 
Naphthalene  yellow,  466. 
Naphthalic  acid,  468. 
Naphthazarin,  467. 
Naphthazine,  502. 
Naphthenes,  45,  53,  327. 
Naphthidine,  465. 
Naphthionic  acid,  465. 
Naphtho-acridine,  498. 
Naphtho-anthracene,  477. 
Naphthoic  acids,  468. 
Naphthol-acetyl  ethers,  466. 
Naphthol  dyes,  466. 
Naphthol-sulphonic  acids,  466. 


Naphthol  yellow,  466. 
Naphthols,  356,  401,  466. 
Naphtho-quinolines,  492,  497. 
Naphtho-quinones,  467. 
Naphthylamines,  464,  465. 
Naphthylamine-sulphonic  acids,  465. 
Naphthylene- diamines,  465. 
Narceine,  499. 
Narcotine,  499. 
Neo-paraffins,  43. 
Nerve  substance,  519. 
Neurine,  196. 

Neutralization,  heat  of,  29. 
Neutral  red,  502. 
Nicotidine,  490. 
Nicotine,  490. 
Nicotinic  acid,  487. 
Nigrosines,  503. 
Nitracetanilides,  349,  352. 
Nitranilines,  318,  338,  341,  352. 
Nitranilic  acid,  394. 
Nitric  acid,  constitution,  102. 
Nitric  ether,  99. 
Nitriles,  aromatic,  405. 
Nitriles,  fatty,  107. 
Nitriles,  fatty,  constitution  of,  110. 
Nitro-acetic  acid,  172. 
Nitro-aceto-nitrile,  108. 
Nitro-alizarin,  475. 
Nitro-amido-phenols,  386. 
Nitro-benzaldehydes,  358,  399. 
Nitro-benzene,  305,  338. 
Nitro-benzene-sulphonic  acids,  375. 
Nitro-benzoic  acids,  402,  414. 
Nitro-benzoyl-formic  acid,  424. 
Nitro -bitter-almond-oil  green,  449. 
Nitro-bromo-benzoic  acids,  418. 
Nitro-camphor,  510. 
Nitro-chloro-benzene,  339. 
Nitro-cinnamic  acids,  418. 
Nitro-cinnamic  dibromide,  417. 
Nitro-cumene,  339. 
Nitro-derivatives,  aromatic,  336,  337. 
Nitro-derivatives,  fatty,  99,  100. 
Nitro-diamido-triphenyl-methane,  449. 
Nitro-dibromo-benzenes,  314. 
Nitro-dibromo-ethane,  102. 
Nitro-dimethyl-aniline,  354. 
Nitro-diphenyl,  438. 
Nitro-erythrite,  203. 
Nitro-ethane,  100. 
Nitro-glycerine,  201. 
Nitro-isatin,  433. 
Nitro-malachite  green,  449. 
Nitro-mesitylene,  337,  839. 
Nitro-methane,  100  et  seq. 
Nitro-naphthalenes,  461,  464. 
Nitro-oxybenzoic  acids,  308. 
Nitro-phenols,  318,  338,  382,  385. 
Nitro-phenols,  salts  of,  386 ►  ' 


536 


INDEX. 


Nitro-phenyl-acetylene,  332,  419,  459. 
Nitro-phenyl-lacto-methyl  ketone,  432. 
Nitro-phenyl-propiolic  acid,  419. 
Nitro-phthalic  acids,  429. 
Nitro-propionic  acid,  172. 
Nitro-pseudo-cumeiie,  339. 
Nitro-quinolines,  496. 
Nitro-thiophene,  301. 
Nitro-toluenes,  316,  337,  338. 
Nitro-toluidines,  359. 
Nitro-xylenes,  314,  337,  339. 
Nitrogen  bases  of  the  alcoholic  radicles, 
110. 

Nitrolic  acids,  102. 
Nitrosamines,  115,  347. 
Nitroso-aniline,  353. 
Nitroso-benzene,  339,  368. 
Nitroso-compounds,  see  also  Isonitroso- 

compounds. 
Nitroso-dimethyl-aniline,  341,  350,  354, 

384. 

Nitroso-diphenylamine,  341,  355. 
Nitroso-indole,  436. 
Nitroso-indoxyl,  435. 
Nitroso-methyl-aniline,  347,  354. 
Nitroso-phenol,  384,  393. 
Nitroso -reaction,  the,  354. 
Nitrous  ether,  100. 
Nomenclature  of  the  alcohols,  77. 
Nomenclature  of  the  hydrocarbons,  42. 
Nonanes,  44. 
Nonylene,  46. 
Nonylic  acid,  163. 
Nuclein,  519. 


O 

o=ortho,  see  Ortho -compounds. 
Oak -tannic  acid,  426. 
Octanes,  44. 
Octo-nitrile,  82. 
Octyl  alcohols,  86. 
Octyl-amine,  182. 
Octyl-benzene,  323. 
Octylenes,  46. 

Octylic  acid,  see  Caprylic  acid. 
CEnanthol,  137. 
Oil  of  the  Dutch  chemists,  48. 
"  Oil-forming  gas,"  50. 
Oils,  fatty,  162. 
Oleic  acid,  166. 
Olefines,  46. 
Olein,  162,  202. 
Olibene,  505. 
Opianic  acid,  430. 
Opium  alkaloids,  499. 
Optically  active  compounds,  their  pre- 
paration by  means  of  ferments,  31. 
Orange  II.  and  III.,  S)0,  371. 


Orange,  oil  of,  504. 
Orange  peel,  oil  of,  508. 
Orcein,  390. 
Orchil,  390. 
Orcin,  377,  390. 
Orcinol,  390. 

Organo-metallic  compounds,  126. 
Orsellinic  acid,  390,  425. 
Ortho-acetic  acid,  derivatives  of,  225. 
Ortho-acetic  ether,  199. 
Ortho-acids,  derivatives  of,  175. 
Ortho-compounds,  309,  315. 
Ortho-formic  ether,  149. 
Ortho-leucaniline,  449. 
Osazones,  287,  373. 
Oxal-ethyline,  221. 
Oxalic  acid,  154,  231. 
Oxalic  ether,  112,  232. 
Oxaluric  acid,  279,  281. 
"  Oxalyl,"  229. 
Oxalyl-urea,  281. 
Oxamethane,  233. 
Oxamic  acid,  233. 
Oxamide,  232. 
Oxanthranol,  472,  473. 
Oximes,  142. 
Oximide,  233. 
Oxindole,  434. 
Oxy-acetic  acid,  206,  210. 
Oxy-acids,  aromatic,  403. 
Oxy-acids,  fatty,  206. 
Oxy-alcohols,  aromatic,  400. 
Oxy-aldehydes,  aromatic,  400,  407. 
Oxy-alkyl  bases,  196. 
Oxy-anthracenes,  472. 
Oxy-anthraquinones,  472,  474. 
Oxy-azo-benzene,  368,  371. 
Oxy-azo-compounds,  368  et  seq. 
Oxy-benzaldehydes,  400,  401. 
Oxy-benzoic  acids,  307,  309,  380,  402,  420. 
Oxy-benzyl  alcohols,  400,  401. 
Oxy-butyric  aldehyde,  134,  220 
Oxy-butyric  acid,  206,  217. 
Oxy-caproic  acids,  206,  217 
Oxy-cinnamic  acids,  427. 
Oxy-citric  acid,  247. 
Oxy-diphenylamines,  387. 
"  Oxy-ethyl,"  194. 

Oxy-ethyl-methyl-tetrahydro-pyridine, 
490. 

Oxy-ethyl-sulphonic  acid,  197. 
Oxy-ethylamine  bases,  187,  193  et  seq. 
Oxy-fatty  acids,  206. 
Oxy-haemoglobin,  518. 
Oxy-hydroquinone,  377,  392. 
Oxy-isobutyric  acid,  206,  217. 
Oxy-lepidine,  493. 
Oxy-malonic  acid,  238. 
Oxy-methyl-benzoic  acid,  423. 
Oxy-naphthoquinones,  467. 


INDEX. 


537 


Oxy-nicotinic  acid,  491. 
Oxy-phenyl-acetic  acid,  408,  422. 
Oxy-phthalic  acids,  314,  429. 
Oxy-pyridines,  480,  486. 
Oxy-quinolines,  480,  496. 
Oxy-stearic  acid,  218. 
Oxy-stearic  acid,  sulphuric  ether  of,  218. 
Oxy-succinic  acid,  238. 
Oxy-tetrahydro-cymene,  511. 
Oxy-thio-naphthene,  437. 
Oxy-toluic  acids,  410. 
Oxy-tropine,  490. 
Oxy-valeric  acids,  206,  217. 
Ozokerite,  46. 


P 

2)=para,  see  Para-compounds. 

Palmitic  acid,  162,  163. 

Palmitic  ethers,  175. 

Palmitin,  162,  202. 

Palmitolic  acid,  168. 

Palmitone,  144. 

Palmito-nitrile,  108. 

Palmityl  chloride,  177. 

Papaverine,  499. 

Para-anthracene,  471. 

Para-aldehyde,  136. 

Para-compounds,  see  individually. 

Para-cumaric  acid,  427. 

Para-fuchsine,  450. 

Para-lactic  acid,  216. 

Para-leucaniline,  450. 

Para-rosaniline,  450. 

Para-xylic  acid,  416. 

Parafl&n,  45. 

Paraffins,  35. 

Parabanic  acid,  279,  281. 

Parchment  paper,  293. 

Parvoline,  481. 

Pelargonic  acid,  163. 

Penta-chlor-aniline,  352. 

Penta-chloro-benzene,  332. 

Penta-decane,  34. 

Penta-decylic  acid,  147. 

Penta-methyl-amid o-benzene,  359 . 

Penta-methyl-benzene,  323. 

Penta-methyl-phenol,  377,  388. 

Penta-methylene  derivatives,  295,  296. 

Penta-methylene-diamine,  195,  482,  516. 

Pen ta-m ethyl ene-imine,  482. 

Penta-triacontane,  34. 

Pentanes,  44,  485. 

Pen-thiophene,  301. 

Pepsin,  294,  516. 

Peptones,  516. 

Perbromo-acetone,  144,  822. 

Per-acid  salts,  157. 

Perchloric  ether,  103. 


Perchloro-ethane,  69. 
Perchloro-cther,  92. 
Perchloro-ethylene,  60,  70. 
Perkin  reaction,  the,  408. 
Persulphocyanic  acid,  261. 
Peru  balsam,  397,  413. 
Petroleum,  45,  53,  320. 
Petroleum  ether,  44. 
Peppermint,  oil  of,  510. 
Phaseo-mannite,  289. 
Phellandrene,  506,  509. 
Phenacyl  bromide,  400. 
Phenanthrene,  475,  476. 
Phenanthrene-hydroquinone,  476. 
Phenanthrene-quinone,  477. 
Phenanthrol,  476. 
Phenazine,  501. 
Phenetol,  382. 

Phenol,  305,  307,  362,  374,  381. 
Phenol  blue,  356. 
Phenol-calcium,  381. 
Phenol  carbonate,  383. 
Phenol-carbonic  acid,  salts  of,  383,  421. 
Phenol-disulphonic  acid,  387. 
Phenol,  ethers  of,  382. 
Phenol  methyl  ether,  see  Anisol. 
Phenol-phthalein,  456. 
Phenol-phthaline,  456. 
Phenol-potassium,  381. 
Phenol-sulphonic  acids,  309,  382,  387. 
Phenol-sulphuric  acid,  382. 
Phenol-trisulphonic  acid,  387. 
Phenolic  acids,  402. 
Phenols,  376,  388,  391,  392. 
Pheno-safranine,  503. 
Phenose,  392. 
"Phenyl,"  327. 
Phenyl-acetaldehyde,  399. 
Phenyl-acetic  acid,  403,  415. 
Phenyl-acetylene,  332. 
Phenyl-acridine,  498. 
Phenyl-acrylic  acid,  403. 
Phenyl-alanine,  417. 
Phenyl  alcohol,  381. 
Phenyl-amido-acetic  acid,  416. 
Phenyl-amido-crotonic  ether,  493. 
Phenyl-amido-propionic  acids,  417. 
Phenyl-amine,  340,  350. 
Phenyl-anthracene,  472. 
Phenyl-anthranol,  472,  473. 
Phenyl-bromo-acetic  acid,  445. 
Phenyl-butylene  dibromide,  415,  460. 
Phenyl-butyric  acids,  412. 
Phenyl-carbinol,  396. 
Phenyl-chloracetic  acid,  416. 
Phenyl-cinnamic  acid,  458. 
Phenyl  cyanate,  341,  358. 
Phenyl  cyanide,  see  Benzonitrile. 
Phenyl-dibromo-propionic  acid,  418. 
Phenyl  disulphide,  384. 


538 


INDEX. 


Phenyl-ditolyl-methane,  446. 
Phenyl  ether,  382. 
Phenyl-ethyl  alcohols,  396. 
Phenyl-ethyl-amine,  341. 
Phenyl-ethyl-hydrazine,  372. 
Phenyl-ethyl-sulphone,  375. 
Phenyl-glucosazone,  288. 
Phenyl-glycerine,  396. 
Phenyl-glyoxylic  acid,  424. 
Phenyl-guanidines,  358. 
Phenyl-hydrazine,  372. 
Phenyl-hydrazine-potassium  sulphite, 
372. 

Phenyl-hydrazine-sulphonic  acid,  373. 
Phenyl  hydrosulphide,  382. 
Phenyl-imido-butyric  acid,  358. 
Phenyl-isocrotonic  acid,  418. 
Phenyl  isothiocyanate,  341,  358. 
Phenyl-lactic  acid,  424. 
Phenyl-methyl-carbinol,  397. 
Phenyl-methyl  ketone,  399. 
Phenyl-methyl-pyrazolone,  302. 
Phenyl-methyl-pyrrol,  400. 
Phenyl-naphthalene,  468. 
Phenyl-naphthylamines,  465. 
Phenyl-oxanthranol,  472. 
Phenyl-oxypropionic  acids,  424. 
Phenyl-propiohc  acid,  332,  403,  419. 
Phenyl-propionic  acids,  408,  417. 
Phenyl-propyl  alcohol,  396. 
Phenyl-pyridines,  480,  487. 
Phenyl-quinolines,  480,  497. 
Phenyl  salicylate,  421. 
Phenyl-salicylic  acid,  421. 
Phenyl  sulphide,  374,  384. 
Phenyl  sulphone,  384. 
Phenyl-sulphuric  acid,  383. 
Phenyl-thio-ureas,  341,  358. 
Phenyl-tolyl-amine,  359. 
Phenyl-tolyl-carbinols,  442. 
Phenyl-tolyl  ketones,  445. 
Phenyl-tolyl-methanes,  445. 
Phenyl-tolyls,  438. 
Phenylene  blue,  356. 
Phenylene  brown,  371. 
Phenylene  diamines,  305,  341,  349,  359. 
Phenylene-ethenyl-amidine,  349. 
Phloretic  acid,  513. 
Phloretin,  391,  513. 
Phloridzin,  513. 
Phloroglucin,  321,  377,  391. 
Phloroglucin  tricarboxylic  ether,  321. 
Phloroglucin  trimethyl  ether,  391. 
Phoroglucin-trioxime,  391. 
Phloxin,  456. 
Phorone,  142,  144. 
Phosgene,  268. 
Phosphin,  499. 
Phosphines,  119, 121. 
Phosphlnic  acids,  120, 121. 


Phosphoric  ethers,  120,  121. 
Photographic  developer,  391. 
Phthaleins,  455. 

Phthalic  acids,  305,  314,  405,  428,  429. 

Phthalic  anhydride,  429. 

Phthalide,  424. 

Phthalideins,  472,  473. 

Phthalidines,  472,  473. 

Phthalines,  455. 

Phthalo-nitriles,  375. 

Phthalo-phenone,  455. 

Phthalyl  alcohol,  396. 

Phthalyl  chloride,  429. 

Physical  properties  of  organic  compounds, 
24,  217,  237. 

Physical  isomerism,  217. 
Picolines  480,  482,  485. 
Picolinic  acid,  487. 
Picramide,  353. 
Picric  acid,  382,  385. 
Picrotoxin,  514. 
Picryl  chloride,  339,  385. 
Pimaric  acid,  512. 
Pimelic  acid,  228. 
Pinacoline,  144. 
Pinacone,  190,  191. 
Pinene,  506. 

Pinene  hydrochloride,  507. 
Pipecolein,  488. 
Pipecolines,  489. 
Piperic  acid,  427. 
Piperideins,  488. 
Piperidine,  480,  488. 
Piperidine,  constitution  of,  483. 
Piperine,  488. 
Piperonylic  acid,  425. 
Piperylene,  57,  489. 
Pirylene,  58. 
Pittacall,  454. 
Pivalic  acid,  161. 
Plaister,  163. 

Poly-ethylene  glycols,  193. 
Poly-terpenes,  506. 
Polymerism,  13. 
"  Ponceaux  "  (dyes),  372. 
Populin,  513. 

Position,  determination  of,  in  aromatic 

bi-derivatives,  315. 
Position-isomerism,  93,  317. 
Potassium  carboxide,  322,  392. 
Potassium  cyanate,  258. 
Potassium  cyanide,  254. 
Potassium-diazo-ethane  sulphonate,  118. 
Potassium  ethide,  126. 
Potassium-ethyl-hydrazine  sulphite,  118. 
Potassium  ferricyanide,  255. 
Potassium  ferrocyanide,  255. 
Potassium  methide,  126. 
Prehnldine,  859. 
Prehnitene,  323. 


INDEX. 


539 


Prehnitic  acid,  430. 

Primary,  secondary  and  tertiary  com- 
pounds, 62,  73,  209. 
Prism  formula,  317. 
Propane,  41. 

Propane-tricarboxylic  acid,  245. 
Propane-trisulphonic  acid,  106. 
Propargylic  acid,  167. 
Propargylic  alcohol,  88. 
Propiolic  acid,  167. 
Propione,  144. 
Propionic  acid,  159. 
Propio-nitrile,  108. 
Propionyl-carboxylic  acid,  224. 
Propionyl  chloride,  177. 
Propyl-alcohols,  83. 

Propyl  aldehyde-phenyl-hydrazine,  436. 
Propyl-amine,  113,  114. 
Propyl-benzenes,  318,  323,  330. 
Propyl-benzoic  acids,  410,  417. 
Propyl  bromides,  65. 
Propyl  chlorides,  65. 
Propyl  iodides,  65,  66. 
Propyl-phenols,  388. 
Propyl-pseudo-nitrol,  102. 
Propyl-piperidines,  489. 
Propyl-pyridines,  486. 
Propylene,  51,  61. 
Propylene  bromides,  68. 
Propylene  chlorides,  68. 
Propylene  glycols,  191. 
Protein  substances,  516. 
Protocatechuic  acid,  410,  425. 
Protocatechuic  aldehyde,  400,  401. 
Prussian  blue,  256. 
Prussic  acid,  252. 
Pseudo-butylene,  51. 
Pseudo-cumene,  323,  330. 
Pseudo-cumidine,  341,  359. 
Pseudo-forms,  265,  391. 
Pseudo-indoxyl,  435. 
Pseudo-leucaniline,  449. 
Pseudo-nitrols,  102. 
Pseudo-tropine,  490. 
Ptomaines,  516. 
Purpuric  acid,  283. 
Purpurin,  472,  475. 
Purpuro-xanthine,  472. 
Pyrazine,  491. 
Pyrazols,  302. 
Pyrene,  477. 
Pyridine,  478,  485. 
Pyridine-carboxylic  acids,  480,  487. 
Pyridine-methyl  iodide,  485. 
Pyridine-sulphonic  acids,  480,  486. 
Pyridone,  486. 
Pyrocatechin,  322,  377,  388. 
Pyro-cinchonic  acid,  236. 
Pyro-meconic  acid,  491. 
Pyro-mellitic  acid,  430. 


Pyro-mucic  acid,  298,  300. 
Pyro-racemic  acid,  223. 
Pyro-racemic  aldehyde,  222. 
Pyro-tartaric  acids,  235. 
Pyro-terebic  acid,  166. 
Pyrocoll,  301. 
Pyrogallol,  305,  377,  391. 
Pyrogallol-carboxylic  acid,  426. 
Pyrogallol  dimethyl  ether,  391. 
Pyroxyline,  293. 
Pyrrol,  297,  300. 
Pyrrol-carboxylic  acids,  297,  301. 
Pyrrol  group,  297. 
Pyrrol-potassium,  300,  482. 
Pyrrolidine,  300. 
Pyrroline,  300. 
Pyrrolylene,  57. 


Q 

Quercite,  392. 
Quercitrin,  513. 
Quick  vinegar  process,  156. 
Quinaldine,  480,  492,  496. 
Quinaldine-carboxylic  acids,  480. 
Quinazine,  498. 
Quinazole  compounds,  498. 
Quinhydrone,  390,  393. 
Quinic  acid,  389,  411,  426. 
Quinine,  500. 
Quinine  alkaloids,  500. 
Quininic  acid,  497. 
Quinizarin,  472,  474. 
Quinoline,  351,  478,  495. 
Quinoline-benzo-carboxylic  acids,  497. 
Quinoline-carboxylic  acids,  480,  497. 
Quinoline  group,  491. 
Quinoline-sulphonic  acids,  480,  496. 
Quinoline  yellow,  496. 
Quinolinic  acid,  488. 
Quinone,  350,  351,  384,  392. 
Quinone-carboxylic  acid,  425. 
Quinone  chlorimide,  357,  386,  395. 
Quinone  dichlorimide,  395. 
Quinone-dioxime,  394. 
Quinone-oxime,  393. 
Quinone  phenol-imide,  357. 
Quinone  tetrahydride,  394,  430. 
Quinone-tetrahydro-carboxylic  acid,  425, 
430. 

Quinoxaline,  350,  498. 


R 

Racemates,  242. 
Racemic  acid,  242. 
Radicles,  14,  22. 
Radicles,  mixed,  88. 


540 


INDEX. 


Raffinose,  292. 
Rapinic  acid,  218. 
Rational  formulae,  19. 
Red  prussiate  of  potash,  255. 
"Reduced"  ring,  317. 
Refraction  equivalent,  30. 
Resin  acids,  512. 
Resin  soaps,  511. 

Resinification,"  511. 
Resins,  511. 
Resorcin,  377,  389. 
Resorcin-phthalein,  389,  456. 
Retene,  477.  , 
Rhigolene,  44. 
Rhodanic  acid,  261. 
Rhodizonic  acid,  395. 
Ricinoleic  acid,  167,  218. 
"  Ricinoleic-sulphuric  "  acid,  475. 
Ring  linking,  52,  198,  295,  311. 
Rocellic  acid,  228. 
Roman  oil  of  cumin,  504. 
Rosaniline,  450. 
Rosaniline  blue,  453. 
Rose  de  Bengale,  456. 
Rosolic  acid,  454. 
Rubean  hydride,  252. 
Ruberythric  acid,  474,  513. 
Rufigallic  acid,  472. 
Rufiopin,  472. 
Rufol,  472. 


S 

s=symmetrical,  318. 
Saccharic  acid,  204,  243,  244,  291. 
Saccharimetry,  291. 
Saccharine,  219. 

"Saccharine  "  (from  coal  tar),  415. 
Saccharose,  291. 
Safranines,  351,  503. 
Sage,  oil  of,  506. 
Salicin,  513. 

Salicylic  acid,  305,  411,  420. 

Salicylic  aldehyde,  400,  401. 

Salicylic  methyl  ether,  78,  421. 

Saligenin,  400,  401. 

Salol,  421. 

Santonin,  514. 

Saponification,  95,  98. 

Saponin,  513. 

Sarcine,  284. 

Sarco-lactic  acid,  216. 

Sarcosine,  213. 

Saturated  hydrocarbons,  34. 

Scarlet,  Biebrich,  372. 

Sebacic  acid,  228. 

Secondary  alcohols,  73  et  seq. 

Secondary  compounds,  62,  73,  209. 

Secondary  ring,  317,  391. 


Seignette  salt,  241. 
Selenium  compounds,  97. 
Serine,  219. 
Serum  albumen,  516. 
Shellac,  512. 

Side  chain  isomerism,  318. 
"  Side  chains,"  318,  325. 
Silicium  tetramethyl,  126. 
Silver  cyanide,  254. 
Silver  fulminate,  109. 
Sinapine,  501. 
Sincaline,  196. 
Skatole,  436. 

Skraup  synthesis,  the,  492. 
Soaps,  163. 

Sodio-aceto-acetic  ether,  226. 

Sodio-malonic  ether,  233,  321. 

Sodium  acetanilide,  357. 

Sodium  ethide,  126. 

Sodium  ethylate,  83. 

Sodium  methide,  126. 

Sodium  nitro-prusside,  256. 

Solanine  bases,  501. 

Sorbic  acid,  168. 

Sorbin,  289. 

Sorbite,  204. 

Sparteine,  501. 

Specific  gravity,  23. 

Specific  rotatory  power,  32. 

Spermaceti,  86,  162. 

Sprit  blue,  453. 

Starch,  293. 

Stearic  acid,  162,  163. 

Stearin,  162,  202. 

Stearin  candles,  162. 

Stearolic  acid,  168. 

Stearone,  144. 

Stearoptenes,  504. 

Stilbene,  457. 

Stilbene  dibromide,  457. 

Stilbene-dicarboxylic  acid,  458. 

Storax,  331,  397. 

Structural  formulae,  see  Constitution. 

Strychnine,  500. 

Stycerine,  396. 

Styphnic  acid,  389. 

Styracin,  397. 

Styrene,  331. 

Styrone,  397. 

Suberic  acid,  228. 

"  Substantive  dyes,"  440. 

Substitution,  laws  governing,  317. 

Substitution,  backward,  37. 

Succinamic  acid,  235. 

Succinamide,  235. 

Succinic  acid,  234. 

Succinic  anhydride,  235. 

Succinic  ether,  321. 

Succinimide,  235. 

Succino-succinic  acid,  430. 


INDEX. 


541 


Succino-succinic  ether,  321,  430. 
"  Succinyl,"  229. 
Succinyl  chloride,  235. 
Sugars,  the,  221. 
Sugars,  synthesis  of,  285. 
Sulphanilic  acid,  305,  375. 
Sulphides,  93. 
Sulphine  bases,  96,  97. 
Sulphinic  acids,  aromatic,  374. 
Sulphinic  acids,  fatty,  105. 
Sulpho-acetic  acid,  172. 
Sulpho-benzide,  374. 
Sulpho-benzoic  acids,  402,  415. 
Sulpho-benzoic  imide,  415. 
Sulphonic  acids,  aromatic,  325,  373. 
Sulphonic  acids,  fatty,  105. 
Sulphones,  96. 
Sulphur,  valency  of,  96. 
Sulphuric  acid,  constitution  of,  106. 
Sulphuric  ethers,  103,  104. 
Sulphurous  ethers,  104. 
Sylvane,  300. 
Sylvestrene,  506,  508. 
Sylvestrene  dihydrochloride,  608. 
Syntonin,  517. 


T 

Tallow,  162. 

Tannic  acids,  426. 

Tannin,  411,  426. 

Tanning,  426. 

Tar,  319. 

Tartar,  241. 

Tartar  emetic,  241. 

Tartaric  acid,  240. 

Tartrazine,  245. 

Tartronic  acid,  238. 

Taurine,  197. 

Taurocholic  acid,  519. 

Tautomerism,  266. 

Tellurium  compounds,  97. 

Teraconic  acid,  236. 

Teracrylic  acid,  166. 

Terebic  acid,  240. 

Terephthalic  acid,  429. 

Terephthalic  aldehyde,  399. 

Terpene  hydrochlorides,  see  Pinene. 

Terpenes,  504. 

Terpenylic  acid,  507. 

Terpin  hydrate,  508. 

Terpinene,  508. 

Terpineol,  508. 

Tertiary  alcohols,  73  et  seq. 

Tertiary  compounds,  62,  73,  209. 

Tertiary  hydrogen  atoms,  423. 

Tertiary  ring,  317. 

Tetra-acetylene-dicarboxylic  acid,  238. 
Tetra-amido-benzene,  349. 


Tetra-bromo-ethane,  469. 
Tetra-bromo-di-iodo-eosin,  456. 
Tetra-bromo-dinitro-benzene,  337. 
Tetra-bromo-fluoresccin,  456. 
Tetra-bromo-methane,  69. 
Tetra-bromo-quinone,  394. 
Tetra-chloro-aniHne,  352. 
Tetra-chloro-benzenes,  332. 
Tetra-chloro-indigo,  432. 
Tetra-chloro-methane,  69,  407. 
Tetra-chloro-quinone,  394. 
Tetra-decane,  34. 
Tetra-ethyl-tetrazone,  118. 
Tetra-hydro-naphthylamincs,  464,  465. 
Tetra-hydro-phthalic  acids,  312,  429. 
Tetra-hydro-pyridine,  488,  490. 
Tetra-hydro-quinoline,  480,  496. 
Tetra-iodo-pyrrol,  300. 
Tetra-methyl-amido-benzenes,  359. 
Tetra-methyl-ammonium  compounds, 
117. 

Tetra-methyl-arsenic  compounds,  122. 
Tetra-methyl-benzenes,  323. 
Tetra-methyl-diamido-benzophenone, 

354,  444,  445. 
Tetra-methyl-diamido-diphenylamine, 

341,  356. 

Tetra-methyl-diamido-triphenyl-carbinol, 
449. 

Tetra-methyl-diamido-triphenyl-methane 
449. 

Tetra-methyl-methane,  44. 
Tetra-methyl-quinoline,  497. 
Tetra-methyl-rosaniline,  453. 
Tetra-methylene,  52. 
Tetra-methylene-diamine,  195. 
Tetra-methylene-imine,  300. 
Tetra-nitro -methane,  103. 
Tetra-nitro-naphthalene,  464. 
Tetra-oxy-anthraquinone,  472. 
Tetra-oxy -benzene,  392. 
Tetra-oxy-benzoic  acids,  426. 
Tetra-oxy-quinone,  395. 
Tetra-phenyl-ethane,  459. 
Tetra-phenyl-ethylene,  459. 
Tetrazo-diphenyl  chloride,  440. 
Tetrazones,  118,  373. 
Tetr,olic  acid,  168. 
Thebame,  499. 
Theine,  284. 
Theobromine,  284. 
Theobromic  acid,  162. 
Thiacetamide,  184. 
Thiacet-anilide,  184,  357. 
Thiacetic  acid,  179. 
Thiacetic  ether,  180. 
Thiacetone,  142. 
Thiamides,  184. 
Thiazols,  302. 
Thiazoline,  302. 


542 


INDEX. 


Thio-acids,  179. 
Thio-alcohols,  93,  95. 
Thio-aldehydes,  134. 
Thio-anhydrides,  179. 
Thio-aniline,  351. 

Thio-carbamic  compounds,  274  et  seq. 
Thio-carbamide,  261,  276. 
Thio-carbanilide,  358. 
Thio-carbonic  compounds,  93. 
Thio-carbonyl  chloride,  275. 
Thio-compounds,  93. 
Thio-cyanates,  261,  262. 
Thio- cyanic  acid,  261. 
Thio-cyanic  ether,  262. 
Thio-cyanuric  acid,  263. 
Thio-diglycollic  chloride,  193. 
Thio-diphenylaraine,  355. 
Thio-diphenylamine  dyes,  350,  356. 
Thio-ethers,  93,  96. 
Thio-gly collie  acid,  211. 
Thio-hydantoin,  277. 
Thio-ketones,  142. 
Thio-naphthene,  437. 
Thio-phenols,  382,  383. 
Thio-phosgene,  275. 
Thio-urea,  276. 
Thionine,  356,  360. 
Thiophene,  297  ,  301. 
Thiophene-carboxylic  acids,  297,  299. 
Thiophene  group,  301. 
Thiophthene,  468. 
Thyme,  oil  of,  388,  504. 
Thymene,  505. 
Thymol,  377,  388. 
Thymo-hydroquinone,  890. 
Thymo-quinone,  394. 
Tiglic  acid,  166. 
Tin,  alkyl  compounds  of,  128, 
Tolane,  458. 
Tolidine,  441. 
Tolu,  balsam  of,  397,  412. 
Tolu-hydroquinone,  390. 
Tolu-quinoline,  495. 
Tolu-quinone,  394. 
Tolu-safranine,  503. 
Toluene,  305,  323,  328. 
Toluene,  formation  of,  324. 
Toluene  hydrides,  329. 
Toluene-sulphonic  acids,  376. 
Toluic  acids,  405,  410,  415. 
Toluic  aldehydes,  399. 
Toluidines,  341,  358. 
Toluylene  blue,  502. 
Toluylene-diamines,  341,  360. 
Toluylene  red,  360,  502. 
Tolyl  alcohols,  396. 
Tolyl-aniline,  498. 
Tolylene  glycol,  396. 

Transformations,  molecular,  166,  309,  330, 
365, 


Tri-acetamide,  180. 
Tri-acetyl-benzene,  321. 
Tri-acetin,  198,  202. 
Tri-amido-azobenzene,  371. 
Tri-amido-benzenes,  341. 
Tri-amido-diphenyl-tolyl-carbinol,  450. 
Tri-amido-diphenyl-tolyl-methane,  450. 
Tri-amido-phenol,  386. 
Tri-amido-triphenyl-carbinol,  450. 
Tri-amido-triphenyl-methane,  450. 
Tri-amines,  aromatic,  349. 
Tri-azo-compounds,  370. 
Tri-benzoyl-methane,  459. 
Tri-bromo-benzene,  314,  335. 
Tri-bromo-phenol,  384. 
Tricarballylic  acid,  245. 
Tri-chloro-acetal,  137. 
Tri-chloro-acetamide,  183. 
Tri-chloro-acetic  acid,  172. 
Tri-chloro-acetic  ether,  175. 
Tri-chloro-aceto-acrylic  acid,  322. 
Tri-chloro-aldehyde,  137. 
Tri-chloro-aniline,  351,  352. 
Tri-chloro-benzenes,  332,  335. 
Tri-chloro-phenomalic  acid,  322. 
Tri-chlorhydrin,  69,  70.  • 
Tri-cyanogen,  256,  257. 
Tri-decane,  34. 
Tri-ethyl-alkine,  196. 
Tri-ethylamine,  117. 
Tri-ethyl-benzene,  320,  323. 
Tri-ethyl-phosphine,  121. 
Tri-ethyl-phosphine  oxide,  121. 
Tri-ethylin,  200. 
Tri-glycoUamic  acid,  212. 
Tri-keto-hexamethylene,  391. 
Tri-mellitic  acid,  430. 
Trimesic  acid,  222,  430. 
Trimesic  ether,  321. 
Tri-methylamine,  116. 
Tri-methyl-arsine,  122,  124. 
Tri-methyl-arsine  dichloride,  122. 
Tri-methyl-arsine  oxide,  122. 
Tri-methyl-benzenes,  305,  323,  330. 
Tri-methyl-benzoic  acids,  412. 
Tri-methyl-methane,  41. 
Tri-methyl-oxy ethyl-ammonium  hy drox  - 
ide,  196. 

Tri-methyl-phenyl-ammonium  com- 
pounds, 348,  354. 
Tri-methyl-phosphine,  121. 
Tri-methyl-pyridines,  480. 
Tri-methyl-quinolines,  480. 
Tri-methylene,  52. 
Tri-methylene  bromide,  68. 
Tri-methylene-carboxylic  acids,  295. 
Tri-methylene  compounds,  295. 
Tri-methylene  diamine,  195. 
Tri-nitraniline,  353. 
Tri-nitro-benzene,  337. 


INDEX. 


643 


Tri-nltro-chloro  benzenes,  832,  335. 
Tri-nitro-naphthalene,  464. 
Tri-nitro-phenol,  see  Picric  acid. 
Tri-nitro-triphenyl-carbinol,  447. 
Tri-nitro-triphenyl-methane,  447. 
"Trioses,"  290. 
Tri-oxy-anthraquinone,  472. 
Tri-oxy-benzenes,  377. 
Tri-oxy-benzoic  acids,  425. 
Tri-oxy-cinnamic  acids,  428. 
Tri-oxy-methylene,  135. 
Tri-oxy-pyridine,  483,  486. 
Tri-oxy-triphenyl-methane,  454. 
Tri -phenyl-amine,  341,  355. 
Tri-phenyl-benzene,  438,  441. 
Tri-phenyl-carbinol,  447, 
Tri-phenyl-carbinol-o-carboxylic  acid,  455. 
Tri-phenyl-guanidine,  358. 
Tri-phenyl-methane,  446,  447. 
Tri-phenyl-methane  bromide,  447. 
Tri-phenyl-methane-o-carboxylic  acid, 
455. 

Tri-phenyl-rosaniline,  453. 

Tri-phenyl-rosaniline-sulphonic  acid,  453. 

Triple  bond,  55. 

Tri-quinoyl,  395. 

Tri-thio-carbonic  acid,  275. 

Tropaolines,  370,  371. 

Tropeines,  490. 

Tropic  acid,  411,  424. 

Tropidine,  489. 

Tropilidene,  58,  490. 

Tropine,  490. 

Trypsin,  254,  516. 

Turkey  red,  475. 

Turmeric,  514. 

Turnbull's  blue,  256. 

Turpentine,  504,  506. 

Turpentine,  oil  of,  504,  506. 

Types,  theory  of,  13,  14. 

''Typical"  hydrogen,  73,  153. 

Tyrosine,  411,  422. 


U 

Umbellic  acid,  427. 
Umbelliferone,  427. 
Undecane,  34. 
Undecolic  acid,  168. 
Undecylenic  acid,  166. 
Undecylic  acid,  163. 
Urea,  1,  270. 
Urea,  salts,  etc.,  of,  272. 
Urea,  alkyl  derivatives  of,  272. 
Ureide-acids,  279. 
Ureides,  272,  273,  279. 
Urethane,  270. 
Uric  acid,  281,  283. 


Uric  acid  group,  279. 
Urine-indican,  435. 


V 

1?  =  vicinal,  313. 
Valency,  theory  of,  13. 
Valency  of  sulphur,  96. 
Valeric  acids,  160,  161. 
Valero-nitrile,  108. 
Valerylene,  53,  57. 
Vanillic  acid,  411,  425. 
Vanillic  alcohol,  400,  401. 
Vanillin,  400,  401. 

Vapour  density,  determination  of,  11. 
Vaseline,  46. 
Vegetable  albumen,  516. 
Vegetable  fibrin,  516. 
Vegetable  substances  of  unknown  con- 
stitution, 513. 
Veratrine,  501. 
Veratrol,  389. 
Vesuvin,  369. 
Victoria  green,  449. 
Victoria  orange,  388. 
Vinasse,  79. 
Vinyl-amine,  117. 
Vinyl  bromide,  60. 
Vinyl  chloride,  60. 
Vinyl  compounds,  70,  87,  92. 
Vinyl  sulphide,  97. 
Violaniline,  351,  503. 
Vitellin,  517. 
Vulcanite,  509. 
Vulpic  acid,  459. 


W 

Water  blue,  453. 
"Wax  varieties,  162. 
Williamson's  blue,  256. 
Wine,  81. 

Wine,  spirits  of,  80. 
Wintergreen,  oil  of,  78,  420. 
Wood  spirit,  78. 


X 

Xanthamide,  276. 
Xanthic  acid,  276. 
Xanthine,  281,  284. 
Xantho-protein  reaction,  515. 
Xantho-purpurin,  472, 


544 


INDEX. 


Xylene-carboxylic  acids,  416. 
Xylene  hydrides,  329. 
Xylene -sulphonic  acids,  376. 
Xylenes,  305,  314,  318,  323,  329. 
Xylenols,  377,  388. 
Xylic  acids,  410,  416. 
Xylidines,  341,  359. 
Xylo-quinone,  394. 
Xylorcin,  377,  390. 
Xylyl  chlorides,  332. 
Xylylene  bromides,  832,  460. 
Xylylene-diamines,  360. 


Y 

Yeast,  80,  294. 

Yellow  prussiate  of  potash,  255. 


Z 

Zinc  ethide,  127. 
Zinc  methide,  127. 
Zinc-methyl  iodide,  127. 


